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> Sparkly hematite mineral was used as a flux by copper smelters. Its distinctive appearance may have helped to attract attention from ancient miners and prospe

by Terr_ 1y ago

> 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.

jandrewrogers 1y ago
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. [0] https://en.wikipedia.org/wiki/Supergene_(geology) https://en.wikipedia.org/wiki/Supergene_(geology)
- throwup238 1y ago
  > Amazing hematite crystals mixed with copper with strong assay signs of gold underneath. Any chance we HN rockhounds could get some specimens? 8-)
- pjc50 1y ago
  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.
  - IAmBroom 1y ago
    Leadville Colorado was the site of a very minor gold rush, that mostly produced large piles of lead tailings. Until someone noticed the lead tailings were not lead, but oxidized silver.
- lightedman 1y ago
  "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?
  - jandrewrogers 1y ago
    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. [0] https://en.wikipedia.org/wiki/Bornite https://en.wikipedia.org/wiki/Bornite [1] https://en.wikipedia.org/wiki/Molybdenite https://en.wikipedia.org/wiki/Molybdenite
scoopr 1y ago
> 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 :)
GreenWatermelon 1y ago
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.
- bombcar 1y ago
  "That old Copper++ is worthless, you need to try this Rust"
- card_zero 1y ago
  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.
  - pixl97 1y ago
    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.
cultofmetatron 1y ago
pretty much why gold was probably the earliest worked metals. easy to identify, can be cold worked in a lot of cases. doesn't corrode.

by Terr_ 1y ago

jandrewrogers 1y ago

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. [0] https://en.wikipedia.org/wiki/Supergene_(geology) https://en.wikipedia.org/wiki/Supergene_(geology)

throwup238 1y ago
> Amazing hematite crystals mixed with copper with strong assay signs of gold underneath. Any chance we HN rockhounds could get some specimens? 8-)
pjc50 1y ago
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.
- IAmBroom 1y ago
  Leadville Colorado was the site of a very minor gold rush, that mostly produced large piles of lead tailings. Until someone noticed the lead tailings were not lead, but oxidized silver.
lightedman 1y ago
"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?
- jandrewrogers 1y ago
  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. [0] https://en.wikipedia.org/wiki/Bornite https://en.wikipedia.org/wiki/Bornite [1] https://en.wikipedia.org/wiki/Molybdenite https://en.wikipedia.org/wiki/Molybdenite

scoopr 1y ago

> 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 :)

GreenWatermelon 1y ago

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.

bombcar 1y ago
"That old Copper++ is worthless, you need to try this Rust"
card_zero 1y ago
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.
- pixl97 1y ago
  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.

cultofmetatron 1y ago

pretty much why gold was probably the earliest worked metals. easy to identify, can be cold worked in a lot of cases. doesn't corrode.