How did our aboriginal ancestors discover Iron?
One of the things that fascinates me about bushcraft and survival is how our ancestors discovered new things for the first time and how they made use of them. How did our aboriginal ancestors discover iron is one of the questions that marked a new age in humanity. Iron tools and materials allowed for new hunting and building methods, new ways to cook and expand their communities and iron is one of the things they came across that changed everything.
The iron age started around the world between 1200 BC and 600 BC depending on the region and circumstances, for example the iron age in Britain began around the year 800 BC after it’s assumed travelers from the east made their way to the island and shared their technology, with the earliest known use of iron smelting coming from somewhere in the middle east around the year 1200 BC.
Before iron came along the metal of choice was bronze, which is a combination of tin and copper. At this point people didn’t really have a good understanding of heat and were only able to melt copper and tin as they have low melting temperatures, with tin melting at 231 °C and copper at 1,085 °C, both temperatures were reachable in a roaring fire using coal.
Iron however has a melting point of 1,538 °C, much too hot to reach in a standard fire and it wasn’t discovered until around 800 BC that the temperature could be increased using an enclosed stone smelter with constant blasts of air.
How did our aboriginal ancestors discover iron in the first place?
Iron ore is found in the highest amounts within various types of rock, but since they only had bronze tools to mine with, it was often more trouble to extract than it was worth. Iron itself is far from hard to find and it just so happens to be the fourth most common element in the earths crust by weight so finding it was never a problem, the trick was to find it in a form that could easily be smelted without having to hack away at rocks with bronze tools.
The first iron deposits people used are believed to have come from bogs and marshes or in a form of sand known simply as “iron sand”. If you’ve ever been out in the countryside and seen a small stream with a red coloration to the water or bottom mud then there’s iron nearby. Stream or river iron is normally not worth mining as its already too heavily rusted by the time you get to the source, but bog, marsh and sand iron deposits work differently because they starve the iron of oxygen and stop the rusting process.
(An example of a nearby iron deposit running into a stream, causing the water and mud to turn a rust color.)
When the iron sinks into the mud its protected from the weather and marsh mud is normally much softer than your standard inland mud, allowing the heavy iron ore to sink to a level deep enough to be starved of oxygen and avoid rusting. The outer layer of the ore chunk would rust but the inner layer was protected from water and oxygen by the rusted outer layer and lack of new oxygen, and since there’s no movement within the mud there was nothing to wear off the rusted part and continue the erosion, so the iron just “sat” there until someone scooped it up.
Iron sand is also quite common and contains other elements that stop it from rusting so it can sit openly on the surface. This would have been the preferred form to find iron since it could be dropped straight into the smelter and didn’t require any grinding down like ore did. This early method of finding iron would have only needed to be done in small amounts because as soon as they had iron tools they could simply mine it in larger quantities from rock.
As for how they managed to melt the iron, it could all be done in rather small smelters, with each village normally producing its own iron from a nearby source. The smelter would be made of clay or stone and the walls would be quite thick apart from the main fire opening at the bottom and a couple of small air holes for the bellows to get into. The smelter would be loaded with alternating layers of coal or charcoal followed by a layer of iron and a pair of bellows would be working together to create a constant airflow into the middle. When the temperature reached 1,538 °C the iron would melt and begin to run out of the front opening into the earth.
(Only with a constant flow of air from the bellows could the coal get hot enough to melt iron)
Sometimes there would just be a chunk of hot iron in the bottom of the smelter which would be taken out and hammered straight away, but if the load was quite big then a channel would be dug into the earth so the iron could run out into ingots either side of the channel.
The initial casting of iron would produce something called pig iron which had a very high carbon content making it very brittle, to the point were it was useless to make tools or weapons from because it would just shatter. The iron could be melted again to purify it a bit more before being worked or it would go straight to the smith to start being hammered. One thing people dont realize about these ancient blacksmiths is that they removed a lot of the carbon content by hand, constantly hammering it for hours on end to flatten and fold it, during the process of which the impurities would oxidize and fall off from the outside.
The next time your in the wilderness keep an eye out for signs of rust within water systems or permanent mud spots, and if you should find one there’s a very good chance you could recover a chunk of raw iron from within the surrounding mud. If you have a metal detector they generally go crazy in areas such as this.
