In Kievan, and then in Muscovite Rus, almost until the end of the 16th century, the main raw material base for iron production was swamp and lake ores lying close to the surface. The scientific term they are referred to as "brown iron of organic origin" or "limonite". Today's names of some settlements, tracts and streams still reflect the interest of antiquity in this raw material: Zheleznyaki village, Rudokop reservoir, Rzhavets stream. The unpretentious swamp resource produced iron of a very dubious quality, but it was it that saved the Russian state for a long time.
Characteristics of swamp ore
Ore in swamps is a type of brown iron ore deposited in wetlands on the rhizomes of aquatic plants. In appearance, it usually appears as placers or thick earthy pieces of reddish-brown hues, the composition of which is mostly represented by iron oxide hydrate, and also includes water and various impurities. Not so often in the composition you can find nickel oxide, chromium, titanium or phosphorus.
Swamp ores are poor in iron content (from 18% to 40%), buthave one indisputable advantage: the smelting of metal from them occurs at a temperature of only 400 degrees Celsius, and 700–800 degrees can already produce iron of acceptable quality. Thus, production from such raw materials can be easily established in simple furnaces.
Swamp ore is widespread in Eastern Europe and accompanies temperate forests everywhere. The southern border of its distribution coincides with the southern border of the forest-steppe. In the steppe zones, iron ore of this type is almost absent.
Through the pages of history
Swamp ore prevailed over vein ore for a long time. In ancient Russia, for the manufacture of iron products, they resorted to ore collected in swamps. They took it out with a scoop, removing a thin layer of vegetation from above. Therefore, such ore is also known as "turf" or "meadow".
Extraction of iron from swamp ore was a purely rural craft. Peasants went out to fish, as a rule, at the end of the summer season and in early autumn. When searching for ore, a wooden stake with a pointed end was used, which was used to break through the top layer of turf, plunging it to a shallow depth of 20-35 centimeters. The results of the search for miners were crowned with a certain sound produced by the stake, and then the extracted rock was determined by the color and taste of the piece. It took up to two months to dry the ore from excess moisture, and in October it was already calcined on fires, burning out various impurities. The final smelting was carried out in winter in blast furnaces. Secrets of how to get swamp ore,handed down and preserved for generations.
It is interesting that in the Old Russian language the lexeme "ore" was used in the meaning of both ore and blood, and the derivative "ore" was a synonym for "red" and "red".
Ore formation
In 1836, the German geologist H. G. Ehrenberg first formulated the hypothesis that the growing bottom sediments of brown iron ore in the swamp are the result of the vital activity of iron bacteria. At the same time, despite the free development in the natural environment, this main organizer of bog ore still cannot be cultivated in the laboratory. Its cells are covered with a kind of sheath of iron hydroxide. Thus, in water bodies, through the development and vital activity of iron bacteria, a gradual accumulation of iron takes place.
Scattered particles of iron s alt from the primary deposit pass into the groundwater and, with a significant accumulation, settle in loose shallow sediments in the form of nests, buds or lenses. These ores are found in low-lying and very humid places, as well as in the valleys of rivers and lakes.
Another factor influencing the formation of bog ore is a series of redox processes in the overall development of the bog system.
Deposits
The largest swamp ore deposits in Russia are located in the Urals, where the total reserve of all deposits is about 16.5 million tons. Brown iron ore of organic origin contains iron from 47% to 52%, the presence of alumina andsilica is in moderate limits. Such ore is beneficial for smelting.
In the Karelian Republic, in the Novgorod, Tver and Leningrad regions there are deposits of goethite (iron oxide hydrate), which is concentrated mostly in swamps and lakes. And although it contains many unnecessary impurities, the ease of extraction and processing made it economically viable. The volumes of lake ore are so significant that at the iron-smelting plants of the Olonets District in 1891, the extraction of these ores reached 535,000 pounds, and 189,500 pounds of cast iron were smelted.
Tula and Lipetsk regions are also rich in brown iron ores of swamp genesis. Iron in the composition ranges from 30-40%, there is a high content of manganese.
Loot Features
Swamp ore is hardly considered a mineral these days and is of little interest for the development of local industry. And if for metallurgy the insignificant thickness of ore-bearing layers is of no value, then for a home amateur hobby they are just right.
In nature, such ore is found in various types and qualities, from voluminous beans and small crumbs to a sapropel-like structure. Their deposits are located at the bottom of swamps, in the lowlands and on the slopes of the hills adjacent to them. Experienced fishermen determine the locations by the characteristic rusty water and dark silt on the surface of the swamps, as well as by a number of other signs. Having removed the top layer of soil, often knee-deep in water, and sometimes evenbelt, they extract the "iron earth" of red-red shades. It is worth noting that ore from high places and under birch forests is considered the best, since iron from it will be softer, but harder iron is obtained from ore located under spruce forests.
Further process from time immemorial has not changed much and includes a primitive sorting of raw materials, cleaning from plant residues and grinding. Then the ore is piled on dry places, on the ground or on special wooden decks and left to dry for a while. At the final stage, it is fired to remove the remaining organic matter and sent to the furnaces for smelting.
Practical application
The presence of phosphorus and other metal additives in the composition of swamp ores leads to a decrease in the use of limonite rocks for steel and iron smelting. Metallurgists are increasingly using earthy varieties as raw materials for the manufacture of foundry sands. Recently, swamp ore has become in demand in chemical cleaners; at coke plants, it is used to remove hydrogen sulfide from the air. And in some European countries, it is used to clean household gas. Certain types of brown iron ore are also used for the production of paints and varnishes, in particular ocher and umber.
Such a variety of swamp ore as "brown glass head" in its native state is highly valued by jewelry makers and stone collectors. Its crystals are used to create exquisite jewelry for every taste: pendants, bracelets, pendants, rings andearrings. Limonite goes well with silver.
