> Sparkly hematite mineral was used as a flux by copper smelters. Its distinctive appearance may have helped to attract attention from ancient miners and prospectors.
Every once in a while I pull up some Wikipedia article with idle curiosity of "If I were transported back in time, could I usefully help this get invented?"
One result of this is a helpless appreciation for how complicated it can be to even identify what kind of substance is present without a staggeringly complex dependency-tree of identifying other chemicals, assaying tests, and the economic surplus to use reagents for analysis.
Things could have been very different if iron ore was hard to distinguish.
Absolutely. As luck would have it, many epithermal mineral deposits have both sparkly hematite and copper ore in the same structure. This is a well-known motif in mineral exploration. They show up in the same geography but are separated into different layers. You can find many papers on the structure of these ore bodies. These are known as supergene deposits[0].
The most important features of these deposits is that they act like distillation columns for metals. Due to weathering and associated sulfuric acid, different metals separate out at different layers of the geology. This creates valuable concentrations for mining purposes.
In modern mining, we kind of ignore these structures for iron mining purposes even though they are frequently > 50% iron by mass. If you find such a thing, you are more interested in the gold, silver, copper potential that is capped by an iron-rich gossan mineral. Iron is a cost sensitive commodity, you need to be able to mine it at very high concentrations and scales to be profitable. If that mineral has a pile of gold, silver, etc distilled underneath it, you’ll be more interested in that.
Not all copper comes from these mineral formations but a lot is. Often, the hematite is mixed in with the copper mineral. I have a mineral exploration prospect right now which is essentially this. Amazing hematite crystals mixed with copper with strong assay signs of gold underneath. It is a predictable motif in mineral exploration.
This is similar to the "rare earth tailings" phenomenon, isn't it. A mine is built to extract one metal, the most profitable at that time, and everything else unextracted ends up in mine tailings or refinery slag. But, in addition to truly worthless silicates, that "waste" includes a bunch of other metals at low purity which may eventually be economic to extract.
"Amazing hematite crystals mixed with copper with strong assay signs of gold underneath."
Did you actually assay out anomalous gold concentrations or are you seeing the sulfides and oxides that are associated with gold? If the former, what sort of concentration are you getting?
I have only assayed samples from the iron cap. You would not expect to find much in that part of the formation but it still came in at 1-2g/ton. There is a large area of visually striking bornite[0] that I have not yet been able to properly sample which is roughly the area you would expect the gold to concentrate. It is in the walls of a narrow, deep canyon at high elevation. The region was mined for gold/copper a century ago, so the existence is not surprising.
The location makes access extremely challenging. It requires 3 hours of hiking, assuming you are fit, and borderline technical mountaineering once you get close to the site. The lower parts of the canyon are also under tens of meters of ice most of the year, which creates a separate set of safety issues. When these mountains were prospected in the 1920s, it would have been underneath a deep permanent snow field. I've visited some of the old gold mines in the area for calibration and this deposit appears substantially larger than those.
The discovery was accidental. I was looking for a waterfall I had seen on satellite imagery in the backcountry and came across an enormous chunk of molybdenite[1] while climbing across granite scree. I made several trips to find the source of the molybdenite higher up the mountains, which I never did, but while searching for that I localized a bunch of other beautiful sulfide/oxide mineral specimens to the above canyon. It gives me a great excuse to explore parts of the mountains no one has been into before.
Honesty I know a bunch of people who are burntout climbers and burntout geologists - sounds like a blast. Fun mineralogy with climbing that’s not…super exotic but still fun? I’d pay for it.
Some of those climbs are dangerous though. The Chambless Skarn has a vertical wall of solid epidote you have to scale to reach a massive pocket of world-class hedenbergite, at the top of the mountain. That wall is a few stories tall, and your only grip is the side walls of the rock around you.
> Every once in a while I pull up some Wikipedia article with idle curiosity of "If I were transported back in time, could I usefully help this get invented?"
This reminds me of the book “How to invent everything” by Ryan North, to kind of see the fast-path for many inventions :)
One of the axioms I go by is that people were never stupid. Our ancestors 5000 and 10000 years ago were just as smart , intelligent and curios as we are today.
With regards to metals, I have no doubt someone, be it a kid apprentice or a master smelter, experimented with melting different rocks to see what comes out. After all, if you already know that different rocks spew out different metals (copper, tin, etc..) it logically follows that there may be more.
And then someone, be it the same person or a different person entirely, would've surely conducted experiments. After all, you already have Tin, Copper, and Bronze which combines both of them; all with different properties. Of course someone will want to know how this new shiny metal the smelter spewed out fares compared with other existing ones.
Then some smith will want to try making something with that metal, new things are exciting. Many people here are familiar with the desire to try out a new Programming language or framework just for the sake of it, and a Bronze age smith is no different. Then someone will give that mee Iron sword/knife/axe a try , duel a friend, ruin their bronze weapon, and said friend will be like "holy shit I want an iron sword too it's way too good" and bam you got a meme.
> Then someone will give that mee Iron sword/knife/axe a try , duel a friend, ruin their bronze weapon, and said friend will be like "holy shit I want an iron sword too it's way too good" and bam you got a meme.
Iron is not a superior material to bronze, if anything it's inferior. Iron's either soft or brittle, depending on carbon content, neither of them awesome qualities in a tool or a weapon. Also, iron's considerably more difficult to smelt, and fully melting iron was not possible at the temperatures achievable with Bronze Age technology. Even after you learned that you need to use charcoal and very high temperatures to reduce iron ore, what you got was a spongy mass of very impure iron at the bottom of your furnace that you then had to refine further.
The biggest thing that iron had going for it was logistics. Where there was copper, there was no tin, and vice versa. Sourcing tin required trade routes thousands of kilometers long – no doubt the demand for tin was a large boon to long-distance trade across Europe and Asia, but it made bronze an expensive commodity.
It required new furnace technologies and a millennium worth of experimentation to perfect the art of controlling the carbon content (and what we now know is the crystal structure) of iron-carbon alloys precisely enough to make steel, and in particular steel blades that combine a hard (martensitic) edge and a flexible (austenitic) spine.
(For the record, Dwarf Fortress (unsurprisingly) is one of the few games that get this mostly right.)
Very minor semantic nitpick as a metallurgist, martensitic and austenitic are not terms that distinguish the ductility of the metal, they are ways the atoms organize into crystal structures (which do have an effect on hardness/ductility).
Austenite is one of the high temperature crystal structures of iron, and is not usually seen at room temperature except in certain non-heat-treatable stainless steels, and in highly alloyed steels some small amounts of retained austenite remains that doesn't get the chance to transform due to low cooling rates and suppressed M_f temperatures. Martensite forms by rapidly cooling austenite without giving the atoms the ability to re-organize into their preferred structure (ferrite, pearlite, or cementite depending on the carbon concentration). This transformation actually changes the size of the crystal matrix, which locks in a ton of internal stress as atoms want to move around but can't. All of this internal stress must then be overcome by an external stress to move the atoms around, resulting in a much harder material.
Martensite requires extremely fast cooling rates (on the order of 100s of degrees/second), which is why most carbon steels are quenched to harden them. These cooling rates are only able to be achieved a little ways into the bulk of the material, so you usually end up with a hardened case made of martensite, and a softer more ductile core that is usually pearlite (layers of ferrite [pure iron] and cementite [iron carbide]) that form due to the slower cooling in the core. This is usually actually more desirable than an entirely through hardened piece, as the hard surface can resist wear and indentation, while the soft core increases the ductility and toughness which reduces the risk of fracture.
Thanks, I was a bit confused by the different allotropes. Interesting that the martensite transform naturally only happens on the surface (which as you say is actually desirable) due to the rapid cooling it requires, I didn't know that. But of course it makes sense that quenching doesn't instantly cool the bulk of the workpiece.
One big advantage of iron is that you can forge it. Bronze has to be cast or cold worked (with annealing steps as necessary). You can't forge weld bronze either, so you need to braze/solder parts together. A skilled blacksmith can forge things from iron quickly and with little waste. It's especially important for things like nails and arrowheads that are needed in mass quantities.
Yeah, Cornwall was most famous for its tin, but there was a reasonable amount of copper too - particularly in the Carnon and Tamar valleys.
There were also very productive copper mines around Great Orme in North Wales, which would have only been a couple of days' travel by boat and were frequently visited as part of the same Atlantic Bronze Age trade routes as Cornish tin.
> Our ancestors 5000 and 10000 years ago were just as smart , intelligent and curios as we are today.
That sounds nice but axiomatic egalitarianism might, just might, not be empirically true.
We know that there are vast differences in all modern uniform populations we have tested -- intelligence is normally distributed and the differences between the tails are huge.
We also know that different populations have different distributions -- slightly different standard deviations, sometimes vastly different means.
Why wouldn't that also have been true at the dawn of history and in pre-history?
Since we do now know many alleles that influence intelligence and we roughly know their effect sizes (very small for almost all of them) and since we can actually sequence really old DNA in some cases, we can actually come up with reasonable guesses for how intelligent people were thousands of years ago.
And what do you know? They do differ. Or at least, their allele frequencies do for those alleles that we are pretty sure have an influence on intelligence. Some of them really do seem to have been pretty dim. Others not so dim.
PS: It's difficult to make an iron sword/knife/axe that is better than a bronze one.
> One of the axioms I go by is that people were never stupid.
Or in some cases, "poor, not stupid" [0], where even geniuses had no power or resources to pursue great innovations compared to the immediate priority of Not Starving.
Ideas improve over time. So people in the past have worse ideas. This might include fear of change, and some mythological notion of an eternal golden way of life, which you must dutifully maintain by spending a thousand years not inventing pottery, and if anybody dares to try it, beating them up.
The improvement of ideas over time is a rather complex process.
It's multiple things working together. Typically you have to have an excess of calories which leads to free time in at least part of the population. While the 'fear of change' as gods fault is more of a post ad hoc rationalization of the horizon problem. That is any change in behaviors in the good times could lead to death in the hard times. Moving away from what works has risks.
Every once in a while I pull up some Wikipedia article with idle curiosity of "If I were transported back in time, could I usefully help this get invented?"
One result of this is a helpless appreciation for how complicated it can be to even identify what kind of substance is present without a staggeringly complex dependency-tree of identifying other chemicals, assaying tests, and the economic surplus to use reagents for analysis.
Things could have been very different if iron ore was hard to distinguish.