Collections: Iron, How Did They Make It? Part I, Mining

This week we are starting a four-part look (I, II, III, IVa, IVb, addendum) at pre-modern iron and steel production. As with our series on farming, we are going to follow the train of iron production from the mine to a finished object, be that a tool, a piece of armor, a simple nail, a weapon or some other object. And I want to stress that broad framing: iron was made into more things than just swords (although swords are cool). If you are here wondering how you go from iron-bearing rocks to a sword, these posts will tell you, but they will equally get you from those same rocks to a nail, or a workman’s hammer, or a sawblade, or a pot, or a decorative iron spiral, or a belt-buckle, or any other of a multitude of things that might be produced in iron.

Iron production is a unique topic in one key way. If the problem with farmers is that the popular understanding of the past (either historical or fantastical) renders them effectively invisible – as indeed, it tends to render most ancient forms of production invisible – iron-working is tremendously visible, but in a series of motifs that are almost completely wrong. Iron is treated as rare when it is common, melted in societies that almost certainly lack the furnaces to do so; swords are cast when they should be forged, quenched in ways that would ruin them and the work of the iron-worker is represented as a solitary activity when every stage of iron-working, when done at any kind of scale, was a team job (many modern traditional blacksmiths work alone, often as a hobby; ancient smiths generally did not). The popular depiction is so consistently wrong that it doesn’t really even provide a firm basis for correction. We are going to have to start over, from the beginning.

So this first post is going to focus on mining. Next week we’ll take a look at ore processing, smelting in more detail, along with the pressing issue of fuel. The week after that we’ll look at the basic principles behind forging. And finally in the last week, we’ll ask what one might do if they wanted steel instead of iron. As with the farming posts, there are likely to be some addendum (at least one, on Wootz steel, for sure). Throughout all of this, we are going to look not only at the processes by which these objects were produced, but also the people who did that production.

Via the Smithsonian, a painting of an iron mine by Homer Dodge Martin (c. 1862) at Port Henry, New York. By the 1800s, increases demand for iron ore to fuel the industrial revolution had made larger underground iron mines more common. Here you can actually see the tailings (rock with little or no iron content which is sorted out at the mine) littering the rock face down to the shore.

As with farming, there is a regional and chronological caveat necessary here: my research into metal production (and this, even more than farming, is core to my academic interests) is focused on the Roman world or – more broadly – on the broader Mediterranean and European tradition of metal-working. There are some points where it will be necessary to note different methods or techniques in other parts of the world (early cast iron in China, for instance, or Wootz steel in India). Likewise, I will do my best to capture changes in metal-working techniques in the medieval period. What I am not going to cover in detail is modern steel and iron-working (that is, post-industrial-revolution), though I will occasionally note how it is different (the largest difference, by far, is that modern steel-making approaches the carbon problem from the opposite direction, with processes to remove carbon, instead of processes to add carbon).

I should also note that this post is going to focus on iron-working (and steel-working). Copper and bronze, the other major tool-metals, are quite different (and may get their own series at some point)!

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Bibliography Note at the Outset: For the sake of keeping these posts readable, especially since I don’t have a footnote function here, I am not going to laboriously cite everything at each point of reference, but instead I am going to include a bibliography up-front for the entire series. For the beginner looking to get a basic handle on the pre-modern iron-production process, I think D. Sim & I. Ridge, Iron for the Eagles: The Iron Industry of Roman Britain (2002) offers one of the best whole-process overviews. On technical details of the forging process, note A.W. Bealer, The Art of Blacksmithing (1969), though much of the same may be learned by conversing with traditional blacksmiths. H. Hodges, Artifacts: An Introduction to Early Materials and Technology (1989) is more diffuse, but still has some useful information on metal production.
There is a robust if somewhat aging literature on Roman mining and metallurgy. Of particular note are (in publication order) J.F. Healy, Mining and Metallurgy in the Greek and Roman World (1978); R.F. Tylecote, The Early History of Metallurgy in Europe (1987); R. Shepherd, Ancient Mining (1993); P. Craddock, Early Metal Mining and Production (1995); V.F. Buchwald, Iron and Steel in Ancient Times (2005). Each of these volumes has their own advantages. Healy and Shepherd are more narrowly focused on Greek and Roman antiquity; Healy has the better coverage of processes, Shepherd the better catalog of known metal mining and processing sites in antiquity. Both Tylecote and Craddock have a wider chronological reach; Craddock is in some ways an update of Tylecote, but the former has a stronger focus on artifacts than the latter. Buchwald is narrowly focused on iron (the others all consider at least bronze, if not also non-tool metals) and of course, the most recent. Finding any study on the condition of medieval mine-workers was difficult (being so far out of my field), but note J.U. Nef, “Mining and Metallurgy in medieval Civilisation” in The Cambridge Economic History of Europe, volume 2: Trade and Industry in the Middle Ages, 2nd. ed. (1987): 691-761.
For the particulars of how that iron might be turned into armor, note D. Sim and J. Kaminski, Roman Imperial Armour: The Production of Early Imperial Military Armour (2012) for the Roman period and A. Williams, The Knight and the Blast Furnace: A history of the metallurgy of armour in the Middle Ages & the early modern period (2003). For metallurgy as it fits into mobilization more generally, J. Landers, The Field and the Forge: Population, Production and Power in the Pre-Industrial West (2003) is a peerless starting point.
On the value and trade in metals in the ancient world, of particular note are M. Treister, The Role of Metals in Ancient Greek History (1996) and L. Bray, “‘Horrible, Speculative, Nasty, Dangerous’: Assessing the Value of Roman Iron,” Britannia 41 (2010): 175-185. Both of these have valuable price-data from the ancient world.

Iron Ores

In most video games, if you are looking to produce some iron things, the first problem you invariably have is finding some iron ores. Often iron is some sort of semi-rare strategic resource available in only certain parts of the map, something that factions might fight over. Actually finding some iron might be a serious problem.

Well, I have good news for historical you as compared to video game you: iron is the fourth most common element in earth’s crust, making up around 5% of the total mass of the part of the earth we can actually mine. Modern industry produces – and I mean this very literally – a billion tons (and change) of iron per year. Iron is about the exact opposite of rare; almost all of the major ores of iron are dirt common. And that’s the point.

One of the reasons that the change from using bronze (or copper) as tool metals to using iron was so important historically is that iron is just so damn abundant. Of course iron can be used to make better tools and weapons as well, but only with proper treatment: initially, the advantage in iron was that it was cheap. Now, as we’ll see, while the abundance of iron makes it cheap, the difficulty in working it poses technological problems; that’s why the far rarer and also generally inferior (to proper, work-hardened, heat-treated iron or steel; bronze will often exceed the performance of unalloyed iron) copper and bronze were used first: harder to find, easier to work. We’ll get to the major problems with iron-working in subsequent weeks (they are in the processing, not the mining), but in brief the problems iron has is that it has a much higher melting point and that cast iron is functionally useless. But let’s get back to those sources of iron.

Very small amounts of iron occur on earth as pure ‘native’ metal; the term for this, “meteoric iron” is an accurate description of where it comes from (there is also one known deposit of native ‘telluric iron‘); in practice, the sum total of these iron sources is effectively a rounding error on the amount of iron an iron-age society is going to need and so ‘pure’ iron may be disregarded as a meaningful source of iron.

Via Wikipedia, Hematite, leaving its characteristic red-rust streak. The hematite on the left has a metallic lustre, whereas the hematite on the right has the (more common) earthy lustre.

Instead, basically all iron was smelted from iron ores which required considerable processing to produce a pure metal. There are quite a lot of ores of iron, but not all of them could be usefully processed with ancient or medieval technology. The most commonly used iron ore was hematite (Fe2O3), with goethite (HFeO2) and limonite (FeO(OH)·nH2O) close behind. Rarer, but still used was magnetite (Fe3O4) and siderite (FeCO3). All of these can occur in big rock deposits, but may also occur as ‘bog iron‘ where oxidation occurs in acidic environments (in swamps and bogs) leading to the formation of small clumps of iron-rich material. Many of these ores can be spotted visually by someone who knows what they are doing; hematite can be blackish to reddish-brown but leaves tell-tale red streaks (of rust); goethite’s black-brown color is also fairly recognizable, as is limonite with its burnt yellow-orange hue. We’ll come back to these ores a few times both this week and next, because while they can all yield iron, some of them yield that iron easier than others.

One distinction here is between bog iron and iron in ore deposits. Bog iron is formed when ground-water picks up iron from iron-ore deposits, where that iron is then oxidized under acidic conditions to form chunks of iron minerals (goethite, magnetite, hematite, etc.), typically in smallish chunks. Bog iron is much easier to smelt because it contains fewer impurities than iron ore in rock deposits, but the quantity of iron available from bog iron is relatively low (although actually renewable, unlike mines; a bog can be harvested for iron again after a few decades as the processes which produce the bog iron continue). Because of its low output, bog iron tends to be an important part of the iron supply only when production is relatively low, such as during the Pre-Roman Iron Age in Europe, or the early medieval period.

Via Wikipedia, a piece of limonite ‘bog ore.’ It has limonite’s characteristic burnt brown or yellow color.

But what I want to stress here at the outset is that while the local variety of iron may vary based on conditions, iron ores are sufficiently common that prior to the industrial revolution, it wasn’t generally necessary to trade or transport them over long distances because most areas have deposits. There are some exceptions (Japan is notoriously mineral poor – my limited geological understanding is that this is common in volcanic land formations – and while it does have some iron deposits, they are few and relatively small), but for the most part, getting iron ore was not hard. As we’ll see, timber availability was actually often a more pressing limitation on iron exploitation than the ore itself, but that’s a topic for next week.


First, we have to get all of these ores out of the ground. Finding ore in the pre-modern period was generally a matter of visual prospecting, looking for ore outcrops or looking for bits of ore in stream-beds where the stream could then be followed back to the primary mineral vein. It’s also clear that superstition and divination often played a role; as late as 1556, Georgius Agricola feels the need to include dowsing in his description of ore prospecting techniques, though he has the good sense to reject it.

As with many ancient technologies, there is a triumph of practice over understanding in all of this; the workers have mastered the how but not the why. Lacking an understanding of geology, for instance, meant that pre-modern miners, if the ore vein hit a fault line (which might displace the vein, making it impossible to follow directly) had to resort to sinking shafts and exploratory mining an an effort to ‘find’ it again. In many cases ancient miners seem to have simply abandoned the works when the vein had moved only a short distance because they couldn’t manage to find it again. Likewise, there was a common belief (e.g. Plin. 34.49) that ore deposits, if just left alone for a period of years (often thirty) would replenish themselves, a belief that continues to appear in works on mining as late as the 18th century (and lest anyone be confused, they clearly believe this about underground deposits; they don’t mean bog iron). And so like many pre-modern industries, this was often a matter of knowing how without knowing why.

Via the British Museum, a drawing (c. 1590-1600) of mining activity, showing the use of hand-tools to mine ore in an open mine (although note the tunnel in the upper right).

Once the ore was located, mining tended to follow the ore, assuming whatever shape the ore-formation was in. For ore deposits in veins, that typically means diggings shafts and galleries (or trenches, if the deposit was shallow) that follow the often irregular, curving patterns of the veins themselves. For ‘bedded‘ ore (where the ore isn’t in a vein, but instead an entire layer, typically created by erosion and sedimentation), this might mean ‘bell pitting’ where a shaft was dug down to the ore layer, which was then extracted out in a cylinder until the roof became unstable, at which point the works were back-filled or collapsed and the process begun again nearby.

All of this digging had to be done by hand, of course. Iron-age mining tools (picks, chisels, hammers) fairly strongly resemble their modern counterparts and work the same way (interestingly, in contrast to things like bronze-age picks which were bronze sheaths around a wooden core, instead of a metal pick on a wooden haft).

For rock that was too tough for simple muscle-power and iron tools to remove, the typical expedient was ‘fire-setting,’ which remained a standard technique for removing tough rocks until the introduction of explosives in the modern period. Fire-setting involves constructing a fuel-pile (typically wood) up against the exposed rock and then letting it burn (typically overnight); the heat splinters, cracks and softens the rock. The problem of course is that the fire is going to consume all of the oxygen and let out a ton of smoke, preventing work close to an active fire (or even in the mine at all while it was happening). Note that this is all about the cracking and splintering effect, along with chemical changes from roasting, not melting the rock – by the time the air-quality had improved to the point where the fire-set rock could be worked, it would be quite cool. Ancient sources regularly recommend dousing these fires with vinegar, not water, and there seems to be some evidence that this would, in fact, render the rock easier to extract afterwards.

Plate from Agricola’s De Re Metallica (1556) showing the fire-setting technique (below), with the use of a ventilation shaft (top right) to keep the air at least a little breathable.

By the beginning of the iron age in Europe (which varies by place, but tends to start between c. 1000 and c. 600 BC), the level of mining sophistication that we see in preserved mines is actually quite considerable. While Bronze Age mines tend to stay above the water-table, iron-age mines often run much deeper, which raises all sorts of exciting engineering problems in ventilation and drainage. Deep mines could be drained using simple bucket-lines, but we also see more sophisticated methods of drainage, from the Roman use of screw-pumps and water-wheels to Chinese use of chain-pumps from at least the Song Dynasty. Ventilation was also crucial to prevent the air becoming foul; ventilation shafts were often dug, with the use of either cloth fans or lit fires at the exits to force circulation. So mining could get very sophisticated when there was a reason to delve deep. Water might also be used to aid in mining, by leading water over a deposit and into a sluice box where the minerals were then separated out. This seems to have been done mostly for mining gold and tin.

Via Wikipedia, a digram of the Roman water-wheel based drainage system for raising water from the Rio Tinto mines. While the Rio Tinto mines do actually have iron ore (indeed, it is what makes the Rio, Tinto, that is, the river red), the Romans mostly mined for copper, silver and gold there; iron exploitation, as far as I am aware, only occurs later on the site. These wheels were constructed in series, each set raising the water up to the level of the top of the wheel, where it then flowed into the next set of wheels. They were turned by muscle power, with workers in the turning them, hamster-wheel style.

But I don’t want to get too deep into this, because almost none of this fancy complexity was used in iron mining. Remember iron? This is a post about iron. As you will recall, iron’s great advantage is that iron ores are relatively abundant, which meant that it was rarely necessary or worthwhile to construct complex mining works to extract it. Only very rich ores would induce pre-modern miners into engaging in deep underground mining for iron; for the most part, it simply wasn’t worth the effort. One of these days, we might talk about the production chain for gold or silver or copper, which were worth the kind of effort to set up complex drainage and ventilation systems.

Instead, iron was generally mined in simple open-pit mines or trenches (if following a shallow vein), using a mix of fire-setting and iron hand-tools. There are some instances of more complex works chasing veins of particularly rich iron ores; my understanding is that there was Roman underground mining of iron in Noricum, for instance, after c. 15 B.C. or so. But the primary iron-mining site for Roman Italy, Elba (which has been estimated to produce a truly staggering 10,000,000 tons per year of ore for several centuries during the Republic; Diodorus (5.13.1) reports that the fires of the smelters were so continuous that the island ended up known as ‘the smokey island’ – Aethaleia – because it was always wreathed in smoke) was, as Healy notes (91) entirely opencast save for one small gallery. As far as I can tell, the bulk of pre-modern iron mining in all periods was done in open-pit (or ‘opencast’) mines. That makes simple all sorts of otherwise complicated problems with ventilation, drainage or ore extraction. Large iron mines of this sort could have several thousands of workers doing this, but smaller operations were also common; there doesn’t seem to really have been a standard size for an iron-mine.

Via Wikipedia, a modern open-pit mine in Australia. An ancient open-pit mine wouldn’t be this large, but would follow the same basic form, including the stepped sides. It’s actually hard to find decent pictures of pre-modern open-pit mines; they don’t seem to have interested artists and because they sit on the surface (often in areas where further mining was subsequently done) they’re exposed to construction, erosion and foliage which tend to obscure older mining works.

So to recap, our iron tool begins its life as a vein or bed of iron-rich ore. Our miners, detecting this ore probably by where it outcrops to the surface, have most likely constructed an open-pit mine to extract it. Bit by bit, using shovels for the soil and then picks, hammers and chisels for the rock underneath, the non-metal-bearing rock is cleared away to expose to the ore itself. The ore is then cleared in much the same manner. Where it is stubborn, the miners set fires over the rock or against the sides of their pits to shatter the stone for easier removal. Apart from this fire-setting, all of the energy to hew our bit of hematite or limonite or what have you out of the ground is provided by human muscle. Once extracted, the ore is loaded into baskets (probably wicker-work, but the exact basket depends on where we are) and manually hauled out of the pit to the surface.


What about the fellows who did all of this work? As always, it depends a fair bit on the period and the place. Essentially the problem that miners faced was that while mining could be a complex and technical job, the vast majority of the labor involved was largely unskilled manual labor in difficult conditions. Since the technical aspects could be handled by overseers, this left the miners in a situation where their working conditions depended very heavily on the degree to which their labor was scarce.

Plate from Agricola’s De Re Metallica (1556), showing a set of picks and chisels. Although these are from the 16th century, they have the same basic form as their earlier Roman equivalents.

In the ancient Mediterranean, the clear testimony of the sources is that mining was a low-status occupation, one for enslaved people, criminals and the truly desperate. Being ‘sent to the mines’ is presented, alongside being sent to work in the mills, as a standard terrible punishment for enslaved people who didn’t obey their owners and it is fairly clear in many cases that being sent to the mines was effectively a delayed death sentence. Diodorus Siculus describes mining labor in the goldmines of Egypt this way, in a passage that is fairly representative of the ancient sources on mining labor more generally (3.13.3, trans Oldfather (1935)):

For no leniency or respite of any kind is given to any man who is sick, or maimed, or aged, or in the case of a woman for her weakness, but all without exception are compelled by blows to persevere in their labours, until through ill-treatment they die in the midst of their tortures. Consequently the poor unfortunates believe, because their punishment is so excessively severe, that the future will always be more terrible than the present and therefore look forward to death as more to be desired than life.

It is clear that conditions in Greek and Roman mines were not much better. Examples of chains and fetters – and sometimes human remains still so chained – occur in numerous Greek and Roman mines. Unfortunately our sources are mostly concerned with precious metal mines and those mines also seem to have been the worst sorts of mines to work in, since the long underground shafts and galleries exposed the miners to greater dangers from bad air to mine-collapses. That said, it is hard to imagine working an open-pit iron mine by hand, while perhaps somewhat safer, was any less back-breaking, miserable toil, even if it might have been marginally safer.

Plate from Agricola’s De Re Metallica (1556), show the initial crushing of ore as the first stage of ore dressing. You can see the sort of back-breaking labor this would be, especially to do in long shifts. The workers here wear protection over their shins to avoid being injured by the splintering rock.

Conditions were not always so bad though, particularly for free miners (being paid a wage) who tended to be treated better, especially where their labor was sorely needed. For instance, a set of rules for the Roman mines at Vipasca, Spain provided for contractors to supply various amenities, including public baths maintained year-round. The labor force at Vipasca was clearly free and these amenities seem to have been a concession to the need to make the life of the workers livable in order to get a sufficient number of them in a relatively sparsely populated part of Spain.

The conditions for miners in medieval Europe seems to have been somewhat better. We see mining communities often setting up their own institutions and occasionally even having their own guilds (for instance, there was a coal-workers guild in Liege in the 13th century) or internal regulations. These mining communities, which in large mining operations might become small towns in their own right, seem to have often had some degree of legal privileges when compared to the general rural population (though it should be noted that, as the mines were typically owned by the local lord or state, exemption from taxes was essentially illusory as the lord or king’s cut of the mine’s profits was the taxes). It does seem notable that while conditions in medieval mines were never quite so bad as those in the ancient world, the rapid expansion of mining activity beginning in the 15th century seems to have coincided with a loss of the special status and privileges of earlier medieval European miners and the status associated with the labor declined back down to effectively the bottom of the social spectrum.

(That said, it seems necessary to note that precious metal-mining done by non-free Native American laborers at the order of European colonial states appears to have been every bit as cruel and deadly as mining in the ancient world.)

Georgius Agricola, describing mining in the 16th centuries, gives a sense of the hours miners worked and the pay they received, noting that in many cases miners were forced to pull multiple consecutive 7-hour shifts just to survive, with the mine itself being worked around the clock when necessary:

Since I have mentioned the shifts, I will briefly explain how these are carried on. The twenty-four hours of a day and night are divided into three shifts, and each shift consists of seven hours. The three remaining hours are intermediate between the shifts, and form an interval during which the workmen enter and leave the mines. The first shift begins at the fourth hour in the morning and lasts till the eleventh hour; the second begins at the twelfth and is finished at the seventh; these two are day shifts in the morning and afternoon. The third is the night shift, and commences at the eighth hour in the evening and finishes at the third in the morning. The Bergmeister does not allow this third shift to be imposed upon the workmen unless necessity demands it. In that case, whether they draw water from the shafts or mine the ore, they keep their vigil by the night lamps, and to prevent themselves falling asleep from the late hours or from fatigue, they lighten their long and arduous labours by singing, which is neither wholly untrained nor unpleasing. In some places one miner is not allowed to undertake two shifts in succession, because it often happens that he either falls asleep in the mine, overcome by exhaustion from too much labour, or arrives too late for his shift, or leaves sooner than he ought. Elsewhere he is allowed to do so, because he cannot subsist on the pay of one shift, especially if provisions grow dearer. [emphasis mine]

Agricola’s mine-workers (note that the translation I linked to uses the word ‘miner’ to mean essentially ‘mine-owner’ whereas ‘workman’ is the word used when Agricola means actual mine-laborers) live in a barracks next to the shift house. While Agricola insists that mining is not so perilous as often believed, it is impossible not to note the sheer number of references to accidents which might befall workmen, from cave-ins to falling down ladders to drowning in undrained water, to death by poisonous fumes or bad air, to a note that mine workmen are peculiarly subject to disease.

One might wonder, even with amenities or small legal privileges, why anyone would sign up for this kind of work. Obviously, non-free miners sent to the mines either as enslaved or convict labor had no choice, but as noted even in the ancient world, there seem to have been a significant number of free miners as well. The supply of desperate people willing to work in such a dangerous job becomes more understandable when we think about the structure of the agricultural economy around these mines: opportunities for wage labor were few, so for individuals who found themselves without any land of their own, economic options to survive were limited. The rural or urban poor were mostly not in a position to acquire the skills necessary to work as craftsmen (such skills were generally passed down through apprenticeship systems and often restricted by professional societies like guilds or collegia). Indeed, the tendency of cities to accumulate unemployable laborers seems to have been a major motivator for many of the large-scale state building projects (like those of Pericles, or Augustus), effectively as ‘jobs programs’ at state expense; that such projects seem to have always found large and ready labor forces is telling. This inefficiency, an economy not well organized to effectively employ surplus labor, is a common feature of pre-modern economies, creating a ready supply of people desperate enough to do things like work in the mines merely to eat.

Meanwhile, mines were effectively never owned or operated by the miners themselves. While we occasionally see periods where private ownership of mines is common (there seems to have been a fair bit of this in the Roman Republic) in practice, mining seems to have been a state-dominated enterprise in both the ancient and medieval world. Typically, the ruler (king, lord, emperor, etc) owned the mine itself and appointed an administrator to oversee it for him. The Athenian state seems to have owned and controlled the silver mines at Laurium; oversight, operations and contracting were supervised by a board of poletai appointed from the citizenry. Mines in the Hellenistic kingdoms seem to have generally been the property of the king personally and mining in pre-Roman Gaul was apparently owned by the Gallic nobility. Roman mines during the imperial period were almost all part of the fiscus (the personal property of the emperor which functioned as a sort of second treasury). Actual on-the-ground administration of the mines varied, sometimes run by conductores or procuratores appointed by the state, sometimes contracted out to private government contractors, the publicani (this more commonly in the Republic).

All Dressed Up

Once our ore reaches the surface (or is removed from its open pit) it is not immediately ready for smelting, but has to go through a series of preparatory steps collectively referred to as ‘dressing’ to get the ore ready for its date with the smelter (note: it seems to me that roasting is sometimes included in ore dressing and sometimes not; we’ll talk about it next week).

Ore removed from the mine would need to be crushed, with the larger stones pulled out of the mines smashed with heavy hammers (against a rock surface) in order to break them down to a manageable size. The exact size of the ore chunks desired varies based on the metal one is seeking and the quality of the local ore. Ores of precious metals, it seems, were often ground down to powder, but for iron ore it seems like somewhat larger chunks were acceptable. I’ve seen modern experiments with bloomeries (which we’ll get to next week) getting pretty good results from ore chunks about half the size of a fist. Interestingly, Craddock notes that ore-crushing activity at mines was sufficiently intense that archaeologists can spot the tell-tale depressions where the rock surface that provided the ‘floor’ against which the ore was crushed have been worn by repeated use.

Plate from Agricola’s De Re Metallica (1556), different kinds of ore-washing going on at a mine, with ore being jigged.

Ore might also be washed, that is passed through water to liberate and wash away any lighter waste material. Washing is attested in the ancient world for gold and silver ores (and by Georgius Agricola for the medieval period for the same), but might be used for other ores depending on the country rock to wash away impurities. The simple method of this, sometimes called jigging, consisted of putting the ore in a sieve and shaking it while water passed through, although more complex sluicing systems are known, for instance at the Athenian silver mines at Laurium (note esp. Healy, 144-8 for diagrams); the sluices for washing are sometimes called buddles. Throughout these processes, the ore would also probably be hand-sorted in an effort to separate high-grade ore from low-grade ore.

Greek artwork showing miners at work. The man on the right is mining with a pick, the leaning man in the center appears to be hand-sorting ore into a basket, while the two on the left lift it out of the mine. The large hanging amphora in the center is an oil-lamp.

It’s clear that this mechanical ore preparation was much more intensive for higher-value metals where making sure to be as efficient as possible was a significant concern; gold and silver ores might be crushed, sorted, washed and rewashed before being ground into a powder for the final smelting process. Craddock presents a postulated processing set for copper ore for the Bronze Age Timna mines that goes through a primary crushing, hand-sorted division into three grades, secondary crushing, grinding, a winnowing step for the low-grade ore (either air winnowing or washing) before being blended into the final smelter ‘charge.’

As far as I can tell, such extensive processing for iron was much less common; in many cases it seems it is hard to be certain because the sources remain so focused on precious metal mining and the later stages of iron-working. Diodorus describes the iron ore on Elba as merely being crushed, roasted and then bloomed (5.13.1) but the description is so brief it is possible that he is leaving out steps (but also, Elba’s iron ore was sufficiently rich that further processing may not have been necessary). In many cases, iron was probably just crushed, sorted and then moved straight to roasting, which we will cover next week.

Conclusion: From Large Rock to Slightly Smaller Rock

I realize the reader may be a bit disappointed that we have spent all of this time to get our iron ore from being in the ground in a very large rock, to hewn out of the ground into a slightly smaller, but still large rock, to smashed (and possibly washed) into a small rock, which still doesn’t get us very close to any kind of metal. One assumes ancient miners were also disappointed at just how much effort it took to force the earth to give up its bounty.

And we are not, in most cases, about the leave the mining site either. Iron ore, even crushed, is terribly heavy and bulk and as we’ll see next week, the ratio of metal to useless rock really favors useless rock. Consequently, if you could do the entire smelting process at the mine, you did, rather than transport so much of that useless rock far away only to have it turned into slag there.

But there’s a larger shift that’s going to happen in our processing next week, because we’re going to begin applying heat. And that means we’re going to need fuel. Lots of fuel, it turns out. Lots and lots of fuel. So, next week: roasting and smelting. We’re going to let a thousand iron flowers bloom (a pun so bad it could make you, like Diodorus’ miners, wish for death).

98 thoughts on “Collections: Iron, How Did They Make It? Part I, Mining

  1. Great article, as usual. I only have one question at the moment. I realize that “meteoric iron” is too rare to be used across a society in any sort of scale. But one of my buddies told me once long ago that the reason you have so many stories of magic swords falling from the sky is probably some sort of disorted memory about superior tools and weapons being forged from meteoric iron, which would have been a superior quality to what was made by contemporary craftsmanship. Is there any basis to that, or is this just moonshine?

    1. There are a decent number of videos of modern blacksmiths trying to forge something out of meteoric iron, and usually failing spectacularly. Maybe they’re too used to working with relatively homogeneous materials and all the weirdness inside a meteorite throws them for a loop. But it does seem like you’d have to be very lucky to get a meteorite that’s 90%+ iron, and then you’d have to have a bunch of people who aren’t experienced with forging iron to turn it into something usable, since I doubt they’d bother once they figured out how to exploit indigenous iron deposits.

      Anyway, I think it’s possible, but it’d be incredibly rare. You’d need the right sort of meteorite and then you’d need people who were more used to working with copper and bronze to not break it beyond repair.

      1. There’s actually a type of meteorite specifically known as ‘iron meteorites’ which have ninety per cent or more iron content. The main theory is that they were once part of the iron core of a small planetary body or something such, which met with disaster.
        Wikipedia gives a figure of them representing slightly more than 4% of meteorites known to hit the Earth’s surface (and cites ‘The Lunar and Planetary Institute’ and a couple of other websites as its sources.)

      2. Meteoric (and telluric) iron seems to be cold-worked much more often than hot-worked (it’s rather malleable and ductile at room temperature). A blacksmith would ruin it.

        Other than the rust (and chemical) resistance, it was not really better than man-made iron (and there are some interesting indications that some people did in fact manage to make man-made iron decently rust proof – or got lucky with a deposit that had the right impurities). As soon as people started to make their own iron, meteoric iron was no longer used – the rarity presents a stark contrast to iron’s abundance, with no real advantage to it. The products made from meteoric iron were probably superior to copper tools, and perhaps even lower-quality bronze, but not really proper iron tools – which got even more pronounced as people developed heat treatment and all that.

    2. There appears to have been some limited use of meteoric iron in pre-contact North American north of the Rio Grande, most specifically with the Cape York meteorite being used by local Inuit to cold-forge arrow and lance heads. However, it’s also worth noting that Inuit people would have had very limited access to any metal tools, especially at Cape York’s latitude (about that of the Svalbard islands). I’m not sure if archaeologists focusing on the Americas have done many experiments to compare cold-forged meteoric iron with other tool materials.

    3. Even if a society used meteoric iron extensively, they likely wouldn’t know it came from the sky. You find meteorites lying on the ground.

    4. What legends are there of magic swords falling from the sky? I can’t think of any in Greek mythology or Norse mythology.

    5. King Tut had a probably meteoric iron dagger. I believe Terry Pratchett had a meteoric iron sword made for himself, too.

  2. “By the beginning of the iron age in Europe (which varies by place, but tends to start between c. 1000 and c. 600)”

    I’m confused. Are these BC (BCE) or AD (CE)? Is this some notation I haven’t seen before?

    I’d always thought that the idea with building a fire against the rock was to shatter it by the thermal stress when you throw water on it, but you seem to be saying that is secondary. Also, is the vinegar thing the source of Will Cuppy’s snark about Hannibal using vinegar as a high explosive?

    1. I had the same interrogation, but the mention further in the paragraph of ‘the Roman use of screw-pumps’ might indicate that it’s BC/BCE

    2. Dates clarified.

      Firesetting works by shattering the rocks through thermal expansion (since the heated area of rock has no space to expand into), rather than through the stress of sudden cooling, as I understand it. On the Hannibal point, I couldn’t tell you.

    3. It’s possible they would augment fire-setting with throwing water in sieges. If the enemy is already shooting at you, adding the risk of hot chips of stone flying from where the water hit is not much of a concern.
      It is known archaeologically that some masonry city walls from the Bronze Age Near East show marks of fire-setting.

  3. Why would people think that ore regenerates after 30 years? Were they going back and finding ore they had missed before?

    1. I don’t know! Perhaps by mistaken analogy to agriculture, where field fertility restores during a fallow period?

      In any case, it shows up again and again, from the Greek and Roman sources to the early 1700s!

      1. It may be that the theory that ores regrew arose from the premodern and Early Modern ‘scientific’ theories about how rocks came to be, rather than from empiricle observation of mines. Three major ones were they were formed from the action of celestial influences on the Earth and/or the Four Elelments within it, they grew from ‘petrific seeds’ in the same way plants grew from seed, or that a liquid called lapidifying juice circulated through the Earth and turned various substances which it touched to stone ( for example Parascelsus described how this juice could turn sea water into pumice). Info admittedly from a rather old book (Adams, F. D. 1938 The Birth and Development of the Geological Sciences)

        1. Hah! Thanks for asking and answering those, because I was literally just about to ask Dr. Devereaux myself if he was aware of by what purported mechanism this regeneration was supposed to happen. For all the talk about how popular culture and video games have colored our perceptions of how things were in pre-modern times, it’s hilarious to me that people in pre-modern times apparently believed that as per many a strategic video game, resources will respawn if you just wait long enough.

    2. I was reading stuff about alchemy years ago, and they mention mine regeneration belief. Some of it was that the distinction between living matter and non-living matter didn’t exist in the way it does now. Mines were “alive”, sort of, because the Earth was. Like how you always hear about how alchemist either wanted to make gold or to make potions of immortality. To alchemists, these weren’t two different things, it was just about creating perfect versions of living stuff.

    3. Geology seems to be susceptible to myth-making, with the myths (even when accidentally created) often being particularly difficult to dispel. See the Superman III film where towards the end Superman flies into a coal mine, picks up a lump of coal, crushes it in his hand, and moments later opens his hand to show a ‘diamond’. Presumably the original intent of the scriptwriter was ‘superman has synthesised a diamond from a piece of coal’ (which should be problematic enough, outside the context of a film which is essentially about a magic (or pseudo-magic if you prefer) alien-space-knight) but the scene seems to have been seen by a lot of people as ‘superman FINDS a diamond in a piece of coal’, leading to a belief/myth that diamonds are NORMALLY found in coal.
      Several decades on from Superman III, judging from the fact that (at the date of this post) even Wikipedia ( ‘…A common misconception is that diamonds are formed from highly compressed coal. Coal is formed from buried prehistoric plants, and most diamonds that have been dated are far older than the first land plants. It is possible that diamonds can form from coal in subduction zones, but diamonds formed in this way are rare, and the carbon source is more likely carbonate rocks and organic carbon in sediments, rather than coal…’ ) seems to feel it necessary in its diamonds article to specifically call out the diamonds & coal myth, the myth is still apparently going strong.

      But way back before the superman films, people were making wild guesses about the dinosaurs and what could have happened to them, or inventing conflicting versions of ‘where the planet came from’.

      If the guys around the Mediterranean in the first century AD believed regular holes-in-the-ground type ‘mines’ recharged, they may well have had their own Superman III story behind it, from somewhere, and this is an era where the rational explanation for lightning involves a supernatural entity called ‘Jupiter’ (or a cultural counterpart equivalent.)

    4. I know this is a bit on the old side, but I thought I could offer anecdotal evidence at least.
      I’m a rockhound, and like to search for interesting minerals and such, often in places where extensive mining had been done in the past. However, often when you get to a site where mining had been carried out in the past (say, 20-50 years ago), the site has significantly changed.
      Trenches/adits/pits have collapsed, trees have grown, undergrowth has completely taken over the site, etc. In the intervening years, other people may have visited the site, and opened test pits in nearby locations, using the existing pit as a waste pit for their digging, etc.
      All these issues, combined with the possibly imprecise locations of such places in ancient times, mean that a miner might excavate in the vicinity of a previous “exhausted” claim, and (Eureka!!) locate the next or neighboring part of a mineral seam/vein.
      From this could arise the idea that returning to a location after a long time gives the location time to recover/regrow/regenerate.

  4. What have you wrought!

    It’s profoundly weird that labor was so cheap that even extremely simple tasks (crushing the ore and, if necessary for drainage, lifting water) often weren’t done with with machine-power, i.e. wind- or watermills, but muscle. But then, this is an economic argument, and it assumes that people would have used kites for power and traction (and perhaps military reconnaissance), and that where only heat was required (not carbon as a reagent), they would have built parabolic mirrors to avoid the massively inefficient step of photosynthesis.

    Ironworking was held up for a time when the blacksmiths unionized. They would always strike when the iron was hot.

    Lindybeige is also annoyed at completely-wrong depictions of ironworking:
    (Another bit: in the example starting at 3:00, there is a fire on the outside of the mould. Were the filmmakers inspired/confused by Rodman guns, perhaps? That’s the only example I know of where a mould would be heated.)

  5. So that’s what big iron is! I’ve seen the name and wondered but never bothered to look it up .Lawrence Stone’s ‘Crisis of the Aristocracy’ introduced me to the major importance of fuel, ie: wood, in ironworks and how availability could be a real limiting factor.

        1. … Is not someone you have to worry about too much, since it’s probably really brittle and a poor weapon.

  6. Bret:
    ‘…Well, I have good news for historical you as compared to video game you: iron is the fourth most common element in earth’s crust, making up around 5% of the total mass of the part of the earth we can actually mine…’

    The 5% figure it looks to me like you’re using is the ‘percent by weight’ figure which statisticians of these things like to use – which can be horribly misleading as to how ‘present’ iron might be, not least since iron is dense (especially so as compared to the elements above it in the ‘percent by weight’ rankings.)

    Rather than write a mini-essay on geology here, about how the figures are further skewed by a number of complications, I’ll just say that I’m with the video-game developers on this one, in terms of you shouldn’t be able to build an iron mine and start churning ore out anywhere in a medieval Europe-like environment. 🙁

    1. I’ll add though that if (in the pre-modern society of your choice) you have enough slaves to work to death and whole forests to burn (the latter reminds me of one of the Saruman pieces on this site) some iron mineral containing rocks which should otherwise be marginal, at best, might move into the exploitable bracket.

    2. Iron is about twice as heavy per atom as silicon or aluminum, and about 3.5x as heavy as oxygen (the more common ones), so will be maybe 1.5-2% of atoms in the crust (yes, I could look this up, but approximation like this works pretty well.) not as common, but still pretty common, seems enough for a good sized province, kingdom, etc. to have something available.

      1. Except that figure is an ‘average’; due to hydrological and bacteria places, that iron is ‘concentrated’ in some places (e.g. Precambrian banded iron formations in deserts and the outback in Australia (one of those heavily mined modern sources Bret mentions), or up in that former volcanic pile inside the arctic circle at Kiruna in Sweden) whilst being virtually absent from (or spread out in quantities so low as to be unusable even with slave labour – e.g. as microscopically thin films around every grain of ‘sand’ in some desert sandstones) others.

        Yes, it’s absolutely great if you’re sitting on top of something like a banded iron formation – you have all the iron you ever want, and more than enough to sell to others – but if not, you have to hope you’ve got something which got locally enriched by hydrological processes (even if that’s only whatever bog-iron there is), or actually go looking somewhere else for it.
        One of the reasons Germany invaded Norway in WW2 was that they desperately needed all-year-round access to that Swedish ore from Kiruna, and they couldn’t afford to see the British potentially take control of the overland rail route to Narvik and the sea-lanes from there, by which Swedish iron ore was most easily shipped during the winter. (And then France collapsed and the Germans got the (lower quality) oolitic Lorraine iron ore, too, as a bonus, but the Germans didn’t know France would go down like that when they launched the Norway operation.)

        1. ‘…due to hydrological and bacteria places…’
          ‘places’ should be ‘processes’. Missed that one. Fat finger syndrome & auto-correct. 🙁

        2. There’s a pretty big difference between the iron demands of a modern, industrial war-machine and the iron demands of a pre-modern state, even a very large one. Iron deposits sufficient for the latter might be insufficient to the former.

          One estimate for the Roman Empire suggested an empire-wide iron production around 82,500 tons (note, finished iron, note ore; as you’ll see next week, there’s a big difference there) per year. By contrast, German steel production in 1940 was 22,000,000 tons per year; 266 times higher.

          For that reason it is perilous to extrapolate pre-modern iron demands from modern iron-mining. On the one hand, many deposits that can be worked today were inaccessible or uneconomical for pre-modern miners relying on hand-tools. But on the other hand, the iron demands of a modern industrial society are so much higher – multiple orders of magnitude, you will note – that iron deposits that might have sustained a pre-modern society almost indefinitely would today be exhausted by a mid-sized country in a matter of years.

          1. By your own account, the Romans aren’t just going to Elba for iron (which at least is an island they can presumably shift stuff on ships from) for iron, but all the way up to Noricum too. That alone suggests to me that this is not a material which they can just find lying around outside the Rome city gates in quantities which even a ‘pre-industrial’ civilization like Rome needs.

            DHZ (‘The Rock-forming Minerals) lists Goethite as FeO.OH by the way, to correct you on a point. My memory of the specifics of geochemistry is somewhat fuzzy, but the OH being after the dot, instead of lumped in with the other O and the Fe is supposed to be significant in some way (and this is ‘A collection of Unmitigated Pedantry’ after all! 😉 ) The Magnetite being identified as Fe3O4, is probably acceptable unless there’s a way to make both superscript and subscript work simultaneously, so that one of the Fe can be identified as (2+ (superscript)) and the other two as (3+ (superscript)). (I think the point of the superscript values business has to do with other elements replacing them in the crystal structure, but again it’s been ages since I wrestled with (and often lost to) geochemistry.)
            I may venture back into DHZ later, but I caught sight of something about Limonite not actually technically being an independent mineral and have slammed it shut and returned it to its protective storage bag!

        3. It is an “average” and will be more or less concentrated in certain places (why ore mines exist), however, a high concentration means a better chance for a particular random place to have a high concentration somewhere nearby.

          As others are pointing out, historical records back this up, most places seem to have a relatively easy time getting the iron they need.

          1. Mobile telephones are commonplace in many countries today. Does this mean that Coltan deposits can be found all over the world to make essential parts of these mobile telephones? The answer is ‘no’, Coltan deposits cannot be found all over the world. There are a very limited number of deposits, and these are very thoroughly being exploited by governments and mega-corporations, so that everyone else can have Coltan and said governments and mega-corporations can turn for themselves a very nice profit.
            It’s sounding to me as if the Elba and Noricum mines Bret mentions may have been the Rio Tinto Zinc mining mega-corporations of their day, tapping the closest-to-Rome known good deposits, and finding that actually they were good enough to keep large areas of Italy (and possibly beyond) supplied – and no doubt making a tidy profit for whoever had the mining concession (or Imperial Roman equivalent) for them. (Were senators allowed to own mines, or was that sort of activity supposed to be ‘beneath them’ and they had to simply be content with taking, uh, ‘gifts’ from whoever got appointed (no doubt by them)?)

            And again: what on Earth are the Romans doing digging out iron ores all the way up in Noricum if these are minerals which supposedly they are able to find ‘anywhere’? I know the Romans are considered to have had excellent transport and communications systems, but this is still somewhere up in the Alps, as best I can make out, where they were digging, and the Romans did not have heavy goods vehicles with internal combustion engines to move their iron ingots around. Elba, they can stick stuff on a ship and move it anywhere by sea – no problem; but Noricum?

          2. Look More Closely Later, 21st century manufacturing is not a sensible guide to medieval / ancient manufacturing because of our globalised and amazingly efficient transportation networks.

            Mobile phones don’t use coltan, they use the niobium and tantalum mined from coltan. It would be possible to mine these from elsewhere else: Wikipedia lists six other countries that produce some tantalum and another eight that have known deposits. BUT because of our 21st C shipping network and the existing infrastructure, right now it is cheaper to mine coltan in one place and ship all over the world.

            About a decade ago IIRC there were stories about China increasing the prices on some of their “rare earth” minerals and holding the rest of the world hostage, driving up consumer electronic prices, etc. This quickly collapsed when various western governments asked various mining companies “is there anything you could do to save us?” and were told sure, the only reason they weren’t producing these themselves was that the Chinese charged less. In the 21st C, small efficiencies in mining and infrastructure lead to concentration.

            Iron ore itself is not sufficient. Brett has told us that fuel supplies and infrastructure also matter. If the Roman iron mines at Noricum already had both high quality ore and the necessary fuel and infrastructure, then yes the efficient transport networks of Rome (not just mechanical efficiency, but also the social efficiency that you’re less likely to get ripped off by bandits and local tolls) would lead to the same sort of large scaling mining and export.

            The point Bret was making is that compared to bronze, “for the most part, getting iron ore was not hard.”

          3. As I recall from stuff about 19th century metal production, you move iron ore to where the fuel is, which is why steel mills are in Pittsburgh near the coal fields instead of Wisconsin/Minnesota where the iron ore is.

            I think it may be the other way around with copper smelting.

          4. I know, I’m late, but still:

            “what on Earth are the Romans doing digging out iron ores all the way up in Noricum if these are minerals which supposedly they are able to find ‘anywhere’?”

            First of all, ore quality in Noricum was better than most.

            Then, it was easier to dig the ore there and chop down the infinite (at that time) forests of south Germany and Austria to then distribute the stuff along the Danube (where most of the population centers and legion fortresses were back then) than do all the work in Elba, having to move wood there to smelt it (The island was quickly deforested, the original holly oaks that covered the island were gone by the 1st century BC), put the ingots on ships, move them to where they can be worked, ship again the final products and disembark them on the adriatic coast and then move them overland in a mountainous region as the Carpatians or the Balkans.

    3. I’m not aware of any premodern society other than Japan that had difficulty in producing iron weapons and armour.

  7. “there was a coal-workers guild in Liege in the 13th century”

    I’d love to hear more about this! I associate coal use with the Early Modern era, not the Middle Ages. What was it used for, where and how often?

    1. My impression is mostly fuel for heating and cooking, but not generally in metal-working because the coal’s sulfur content was too high and would spoil the metal. I wish I could tell you more, but honestly this is an area where my own knowledge is really thin.

  8. The effects of iron’s commonness were so obvious that Aristotle commented on how the switch meant the change from aristocracy to democracy as more and more people could afford weaponry.

  9. I’ve wondered recently if ethical low-tech mining was even possible, or if civilization rested necessarily on poor exploited labor.

    How does an amphora oil lamp work? AIUI oil lamps are generally shallow due to the viscosity of the oil (and the use of opaque ceramic rather than glass).

    Would waterwheels get used for crushing ore, where handy?

    I wonder if a muscle-powered mill would still be better for the workers than striking rocks directly.


    increases demand for iron ore — increased

    with workers in the turning them

    the 16th centuries

    1. Medieval Europe used water-powered stamping mills. In general, the Romans don’t seem to have exploited water-power as much as medieval people (although they did have a large water-powered flour mill at Barbegal near Arles, and others on the Tiber.

      1. My understanding is that archaeologists have only more recently uncovered ways to locate the remains of Roman mills and have been finding them all over the place throughout the former Empire. They feature in ancient writings and appear to have spread to even backwaters like Britannia. For an old overview see Wilson (2001). “Machines, power, and the ancient economy”:

    2. My list below repeats, with further clarification of where to find the ones in captions, if helpful:
      Caption for iron mine painting: 1800s, increases demand –> 1800s, increased demand
      Caption for Roman water-wheel: workers in the turning them –> workers in them turning them OR workers turning them
      cleared away to expose to the ore –> cleared away to expose the ore
      terribly heavy and bulk and as –> terribly heavy and bulky and, as

  10. ‘which has been estimated to produce a truly staggering 10,000,000 tons per year of ore for several centuries during the Republic’

    ‘One estimate for the Roman Empire suggested an empire-wide iron production around 82,500 tons (note, finished iron’

    Are these numbers consistent? If all the ore came from Elba, that would mean 0.008 of the ore comes out as iron by weight if there’s more ore, less.

    10 million tons of ore a year, over 365 days and 10,000 workers, is 2.7 tons of ore per worker-day. Is that plausible? Do we need more workers?

    1. Yes, the numbers don’t add up.
      From wikipedia:
      – “The typical grade of iron at which a magnetite-bearing banded iron formation becomes economic is roughly 25% iron”
      -“Banded iron formations (BIFs) are sedimentary rocks containing more than 15% iron”
      -“Export-grade DSO ores are generally in the 62–64% Fe range”
      So, even if we assume rather low-grade ore and that some of the iron is lost in the process, that still leaves more than factor 10 to be explained.

      10.000 workers my be a bit on the low side. As a point of comparison, “Carthage must be destroyed” by Richard Miles gives the number of 40.000 slaves for the spanish silver mines in the roman period.

      1. You’re right to point out that the estimates are inconsistent; they come from different sources and are estimated different ways. For my own part, I think it’s likely that the Roman iron consumption figure is the one that is off and real figure might be higher. But it’s hard to say how much higher. A lot of work on the ancient economy is, at best, informed guesswork.

        As for the ratio of iron-ore to finished iron, as far as we can tell, ancient iron-working was a lot less efficient than modern iron-working. From raw ore to finished goods, the estimates range from 8-16% of the mass of the ore ends up in the finished product. Not quite enough to explain the discrepancy, but still a big gap from modern figures.

        It is also worth noting though that these two figures are for different periods. Elba is active during the Roman Republic and seems to be the primary supply of iron for all of Italy. The estimated figure for total consumption is for the empire.

      2. Mining engineer here, enjoying this series…

        I will start by saying that I know very little about ancient mining, but a fair bit of modern practices, and the wikipedia figures are ok rules of thumb for mining today. In general, older mining is at higher grades and closer to surface – the richer, easier orebodies were mined first (within a given area).

        Some iron deposits are so rich, they are pushing the stoichiometric limits, i.e., they are composed of pure iron mineral (hematite or magnetite) – these are the DSO deposits (Direct Shipping Ore, e.g. Mary River Mine in Nunavut). These ores skip some processing steps and can go straight to steel-making.

        As Bret noted (and I’m sure will explain in future installments), the conversion rates of ore to metal are very different now…

    2. “10 million tons of ore a year, over 365 days and 10,000 workers, is 2.7 tons of ore per worker-day. Is that plausible?”

      Shift sixteen tons and whaddya get?
      Another day older and deeper in debt..

      2.7 tons of ore per day is, I would say, entirely possible. One man with a shovel can move one ton (or one cubic yard) of loose soil in one hour.

  11. For a more visual example:
    This episode of Absolute History shows the process by which c. 1500 CE farmers (could have) exploited lead deposits on a very small scale as an additional source of income to pay their taxes.
    Rather notable is the amount of wood used: an almost 2 meter high pile to smelt 2 or 3 small ingots.

    The channel has several series of documentaries following long term experimental archeology, and a lot of the ideas and info from here show up in there as well.

  12. Also, not that 82,000 tons of iron works out to a little more than a kilo per inhabitant of the empire – about one decent pick or a couple of saucepans per year.

      1. I vaguely recall an article looking at standards of living through stories of miracles – a lot of W European saints in 700-900 did miracles like “retrieving a ploughshare that someone had dropped in a river” which implies just how valuable an object an iron ploughshare was in those days…

    1. True – but iron tools are very durable. My parents use some gardening tools that (I think) belonged to their grandparents, and saucepans and knives they’ve had since they were in their early 20s – 40 years ago.

      1. Modern steels last much longer. Also, we don’t put a lot of our stuff to heavy use – you go through a lot of chisels and picks breaking rocks. Also, a lot gets locked away where it cannot be re-used – Romans used iron clamps to hold stone building blocks together, for instance. For whatever reason, iron was much more used in the middle ages (the Catalan forge – an early blast furnace, plus greater use of water power may have had something to do with it).

  13. It looks like the more ubiquitous a practice was the less likely it was to be recorded or even really mentioned, I guess like farming Iron Mining was so common it just faded into the background as a fact of life.
    It’s assumed the reader already understands the practice (or that they think they do) that it would be redundent to bring it up.
    Makes you wonder if any modern system will end up being forgotten entirely because of how foundational it is to society.

    1. Like the famous third shaker. People in England used to have a shaker for salt, one for pepper and one for something else and we don’t know what the third one was.

      Wasn’t even that long ago either.

      1. Wait really! I mean i’m english and i’ve never even heard of that!
        It just shows how all the most mundane things the things we don’t feel the need to mention seem to be what we forget, makes you wonder what was considered such common sense that it was never mentioned.

  14. I have no stake in the iron ore wars, but I’d note that price/ease of access can matter. It could be true both that iron ore is widely available and that particular locations are economically dominant due to quality, access, or nearby smelting infrastructure so you don’t have to ship bulky ore around.

    1. Quality was clearly a factor – Indian and Noricum iron was higher value. But the main constraint was fuel. A low-grade iron deposit near a forest was better than a high-grade one where wood was expensive. Even for finished products, transport was sufficiently expensive that local production persisted until quite recently.

      1. Yes. Fuel access seems to have been a dominant concern. Elba is one of the rare examples were ore was shipped to processing after local fuel ran out (but then, shipping by sea was relatively cheap and the new processing point, Populonia, was right there on the opposite coast).

  15. As far as I can tell, such extensive processing for iron was much less common

    I have heard the slag from ancient Roman mines was used as a source for iron in modern times, which would be evidence for this, but alas I heard it in an internet discussion so I don’t have a citation.

  16. I find it interesting that blacksmiths in mythology seem to normally be one-man shows, even though the actual practice was a team effort.

    1. Hephaestus has Cyclopes as strikers in some mythic portrayals and a set of automatons that also work with him in the Iliad. I’d have to go look for other mythological smiths.

  17. @Bret, I’d really like to hear a breakdown of labor sometime in this series, like how farming mentioned 80%-90% of the population were farmers and discussed the distribution of land between farms. What did the labor ratio look like between the various activities: mining, ore preparation, fuel collection, smelting, etc.?

  18. This is quite an interesting article to one who worked summer vacations on the steel works at Scunthorpe in the UK.
    I am now a retired chemist, proud Scunthonian and Lincolnshire man but still enjoy describing myself as an escaped steel or iron worker out of respect for those I worked with who were a close bunch of amiable guys. I used to stand in as a blacksmiths strike when the real one went on holiday during the summer which despite being hard work was fun and a proud possession is a small decorative brass anvil I have in memory of a small Czech Blacksmith called ”Cass” who taught me a lot. A work colleague of mine was the daughter of a blacksmith and he maintained you were not really moving metal unless you had three strikes working together which could be essential if you wanted to make blooms efficiently (see part two) My paternal grandfather was a keeper of an open hearth furnace and my maternal grandfather was a blast furnace keeper

    I can well sympathize with the miners of old since as an iron works laborer (1969-1973) I spent many hours on the wrong end of a shovel as we put it shoveling iron ore, know by those in the know as ‘shit or muck’. The worst you could hear on being set on was K42, this was the sump of a conveyor belt carrying crushed ore up onto the final crusher in the sequence. It was fed by a belt dropping its charge onto it from above, this made dust or to be more correct a yellow fog of visibility less than 3 feet. Try that for size for eight hours in a COVID mask and goggles, you were calf deep in a yellow ochre colored cement powder trying to load it back onto the rising belt where you had to pour it off your shovel.

    Our charge hand ‘Cockney’ as he was known told me when he started (1960’s) he started in the old open cast mines at a spot called ‘Ashby Ville’ hand loading what was rich iron ore for the vein (40%?) into a 16 ton railway wagon and you had to fill one a shift. He had a very useful term for those on hard work, I use the acronym KBIS for it as it means ”keep buggering in steady”, the only way to do hard labor and survive the day.

    Those among you of a chemical bent may wish to know that we made sinter from a mixture of Northampton shire iron ore and local Scunthorpe iron ore by burning it at red heat with around 10% by weight of pea sized coke. This removed all volatiles from the ore to give sinter which was far more easy to reduce with a low melting free draining slag (see part two).

    ”Stan the blast furnace man” or ”Tommo”

  19. ‘Remember iron? This is a post about iron.’

    I come for the content, I stay for the Alice’s Restaurant references.

  20. Japan’s rich in gold and exported a lot of it to Korea and China, and this blog on samurai stuff talks about the different sources of iron that were found there:

    According to that above blog, post Industrial revolution is when Japanese iron ran thin, but before that Europeans wrote of iron being enough to supply local demands and reject some European traders:

    “”With respect to iron, the Japanese do not posses that metal in such abundance as copper, but they have sufficient to supply their absolute wants; and if the government exchanged with the Dutch, copper for iron, this was not out of necessity, […] If the Japanese had not iron sufficient for their absolute wants, they would certainly set more value on the trade with the Dutch”
    -Recollections of Japan: with Observations on the Geography, Climate, Population, and Productions of the Country by “Vasiliĭ Mikhaĭlovich Golovnin

    Now that blog also says ‘iron was rare pre industrial’ so you can probably help them with their info too.

  21. Thanks for this series of posts; it’s tremendously interesting and helpful. I’m curious as to whether there is any evidence indicating what medieval miners did with the waste materials from this process? (I’m an author looking for a way to explain how one of the steps in the medieval sword-making process might have poisoned a grove of mulberry trees.) Thanks!

    1. See: Tailings pile. They dumped the waste someplace close and convenient. The thing to be aware of in the context of your story is that ‘ore’ doesn’t mean ‘mineral that contains iron and some H, O and C’. Ores can have a wide mix of other fun stuff mixed in. Some of that (like sulfur) can make the water runoff from an iron mine extremely acidic (big issue), Iron ores are also associated with other metal ores of things like lead, cadmium and arsenic. So you should have no problem support a connect between iron production and dead trees.

    2. A common problem with iron ores is “acidic mine drain” (AMD). A previous comment explains that “Rio Tinto” can be translate for “Red River” and this is because the iron compounds drained from the waste dumps:,_cauce_34.jpg
      And about the toxicity, when I was young, country people use to put mine waste or iron slag on rural paths because “nothing grows there”.

  22. Couple of Points:
    Bog Iron forms as an Iron pan and is created by iron being leached out of the soil/clay above. That is why it is assocated with bogs which provide the water logged conditions to produce podsols. It has nothing to do with acid reacting with iron ores.
    You are correct that fire setting only needs the heat from a fire. Experimental archaeology has shown that throwing water onto heated rock does not increase the amount of shattering but can produce explosive shattering.
    Finally while slave and paid miners certainly did exist, there is third possibilty part time miners in communities which specialised in ore production. In this scenario the mining would be done in the agricultural down season and the mines would have been controlled by the local community be that tribe,clan or kingdom etc.

  23. Living in The Netherlands, where most of the economic and industrial activity is now mostly in the west (Holland/Utrecht/Zeeland) it came as a surprise to me to learn that during the early Middle Ages (800 CE till 1100 CE) there was a large Iron Industry in what is now the largest National Park in The Netherlands (de Veluwe). Apparently there were large “veins” of “klapperstenen” (clapping stones) (a form of IJzeroer/Bog Iron) within the sand that was deposited there by the glaciers during the last Ice Age. This is still visible as the fairly large, and broad valleys that were excavated in the sands of the glacial deposits in search of those stones. Also, the first “Industrial” blast furnace (ca. 1650 CE) was in the IJsselvalley where there was both abundant forest and IJzeroer near the rivervalley.

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