As you know, the history of ferrous metallurgy begins around the 12th century BC. Prior to that, people sporadically used meteoric iron, which, as its name implies, was brought to Earth by meteorites that formed at an early stage in the evolution of the solar system.
The real assimilation of iron occurs when people learn to melt it in cheese-blowing ovens.
Modern technologies make it possible to extract iron-rich ores from the earth's crust at depths of hundreds of meters, but our distant ancestors did not possess such technologies. They had to be content with rare deposits of relatively shallow occurrence.
Such deposits, as a rule, were of organic origin - these are traces of the vital activity of colonies of ancient microorganisms - iron bacteria. They are able to oxidize ferrous iron to ferric and use the energy released during this process to assimilate carbon from carbon dioxide or carbonates.
Iron bacteria are extremely widespread in both fresh and sea water bodies, and play an important role in the cycle of iron in nature. Due to their vital activity, a huge amount of deposited iron and manganese ores is formed at the bottom of swamps and seas.
In particular, the so-called Swamp ore, which is a type of brown iron ore, naturally deposited in bogs on the rhizomes of bog plants. Swamp ores contain 20 - 60 percent iron oxide, as well as some iron oxide and manganese oxide. Nowadays, bog ores are considered to be of low quality and unsuitable for industrial development, however, in ancient times and in the Middle Ages, this source of iron was used very widely by man.
