Rare and valuable minerals

What minerals are iron ores?

Iron ore is a rock that contains a natural accumulation of various minerals and necessarily, in one ratio or another, contains iron, which can be smelted from the ore. The components that make up the ore can be very diverse. Most often, it contains the following minerals: hematite, martite, siderite, magnetite and others. The quantitative content of iron contained in the ore varies, on average it ranges from 16 to 70%. Depending on the amount of iron content in the ore, it is divided into several types. Iron ore containing more than 50% iron is called rich. Conventional ores contain no less than 25% and no more than 50% iron. Low-grade ores have a low iron content; it constitutes only a quarter of the total amount of chemical elements included in the total content of the ore. Iron ores that contain a sufficient iron content are smelted into cast iron; for this process it is most often enriched, but it can also be used in its pure form, it depends on the chemical composition of the ore. In order to produce steel, a precise ratio of certain substances is required. This affects the quality of the final product. Other elements can be smelted from ore and used for their intended purpose. In general, all iron ore deposits are divided into three main groups, these are: • igneous deposits (formed under the influence of high temperatures);
• exogenous deposits (formed as a result of sedimentation and weathering of rocks);
• metamorphogenic deposits (formed as a result of sedimentary activity and the subsequent influence of high pressure and temperature). These main groups of deposits can, in turn, be subdivided into some subgroups. Russia is very rich in iron ore deposits. Its territory contains more than half of the world’s iron deposits. The most extensive deposit is the Bakchar deposit. This is one of the largest sources of iron ore deposits not only in the Russian Federation, but throughout the world. This deposit is located in the Tomsk region in the area of ​​the Androma and Iksa rivers. Ore deposits were discovered here in 1960, during the search for oil sources. The deposit spreads over a very vast area of ​​1600 square meters. meters. Iron ore deposits are located at a depth of 200 meters. Bakchar iron ores are 57% rich in iron; they also contain other useful chemical elements: phosphorus, vanadium, gold, platinum, palladium. The volume of iron in enriched iron ore reaches 97%. The total ore reserve at this deposit is estimated at 28,7 billion tons. Technologies for the extraction and development of ore are being improved from year to year. Quarry mining is supposed to be replaced by borehole mining. In the Krasnoyarsk Territory, approximately 200 km from the city of Abakan, in a western direction, the Abagaskoe iron ore deposit is located. The predominant chemical element included in the local ores is magnetite, it is complemented by musketovite, hematite, and pyrite. The total composition of iron in the ore is not that high and amounts to 28%. Active ore mining at this deposit has been going on since the 80s, despite the fact that it was discovered back in 1933. The deposit consists of two parts: Southern and Northern. Every year, an average of just over 4 million tons of iron ore are mined in this place. The total amount of iron ore reserves at the Abas deposit is 73 million tons. In Khakassia, near the city of Abaza in the Western Sayan region, the Abakan deposit has been developed. It was discovered in 1856, and since then ore has been mined regularly. During the period from 1947 to 1959, special enterprises for the extraction and enrichment of ores were built at the Abakan deposit. Initially, mining was carried out using the open-pit method, and later they switched to the underground method, constructing a 400-meter mine. Local ores are rich in magnetite, pyrite, chlorite, calcite, actinolite, and andesite. The iron content in them ranges from 41,7 to 43,4% with the addition of sulfur and zinc. The average annual production level is 2,4 million tons. The total reserve of deposits is 140 million tons. Iron ore mining and processing centers are located in Abaza, Novokuznetsk and Abakan. The Kursk magnetic anomaly is famous for its richest iron ore deposits. This is the largest iron pool in the entire world. More than 200 billion tons of ore lie here. This amount is a significant indicator, because it accounts for half of the iron ore reserves on the entire planet as a whole. The field is located on the territory of the Kursk, Oryol and Belgorod regions. Its borders extend over 160 square meters. km, including nine central and southern regions of the country. A magnetic anomaly was discovered here a long time ago, back in the 000th century, but more extensive ore deposits became possible to discover only in the last century. The richest reserves of iron ore began to be actively mined here only in 1931. This place contains a reserve of iron ore equal to 25 billion tons. The iron content in it ranges from 32 to 66%. Mining is carried out using both open and underground methods. The Kursk magnetic anomaly includes the Prioskolskoye and Chernyanskoye iron ore deposits. Iron is a common element in nature. Its content in the earth’s crust is 4,2%. It only contains more oxygen – 49,7%, silicon – 26% and aluminum – 7,45%. Ore minerals or ores are those mineral masses from which it is economically feasible to extract metals or a necessary element. According to this iron ores are called rocks from which it is economically feasible to smelt iron. The constant change in economic conditions due to the development of ore beneficiation methods and the reduction in the cost of their transportation changes the idea of ​​​​iron ore, since the lower limit of the iron content in it is constantly decreasing. An industrial ore deposit is considered to be an accumulation of ores that is economically feasible to develop. The profitability of this development increases with the increase in the capacity of the field, since investing in the construction of, for example, mines or quarries, housing, communications, is advisable only if the field has been in operation for a sufficiently long time. Experience shows that the exploitation of the iron ore deposit is feasible and has a sustainable prospect with reserves of about 250-500 million tons. Ore consists of ore and ore-forming minerals, gangue and impurities. The extracted element is found in the ore mineral. Ore minerals of iron ores are oxides, carbonates of iron and some other compounds. The main ones are described below. Hematite – has a chemical composition of Fe2O3 – anhydrous iron oxide. Hematite contains 70% iron. The ore formed by hematite is called red iron ore and is the most common type of ore. It is usually characterized by a high iron content and a low content of harmful impurities. A typical deposit of hematite ores is Krivoy Rog. Figure 1 – General view of the hematite mineral Magnetite – has the chemical composition Fe3O4 – magnetic iron oxide containing 72,4% iron. It differs from other industrial iron ore minerals in its magnetic properties, which are lost when heated above 570 o C. Magnetite is a mixed iron oxide FeO*Fe2O3. Ores formed by magnetite are called magnetic iron ores or magnetites. They are less common than hematites, characterized by a high iron content, reduced reducibility, and often accompanied by sulfur. Figure 2 – Type of mineral magnetite Hydrous iron oxides – Fe2O3* nH2O – depending on the value of n, they form different types of oxides, but all the ores they form are called brown iron ores. The following hydrous iron oxides are distinguished:

  • n=0,1 – hydrohematite
  • n=1 – goethite
  • n=1,5 – lemonite, etc.

The most common brown iron ores based on limonite – 2Fe2O3* 3H2O which are called limonite.

Brown iron ores are characterized by a low iron content, are friable, often accompanied by manganese and phosphorus, and have high porosity and reducibility.

Figure 3 – Brown iron ore based on limonite

Siderite – has the chemical composition FeCO3 – iron carbonate. Contains 48,2% iron. The ore formed by siderite is called spar iron ore, or siderite. With significant amounts of clay impurities it can be called clay iron ore. Siderites are much less common than other ores. They are characterized by high reducibility, low iron content due to its insignificant content in the ore mineral and a large amount of waste rock. Under the influence of atmospheric moisture and oxygen, siderites can transform into brown iron ores, since iron (II) oxide in the FeO*CO molecule2 oxidizes and absorbs moisture. Therefore, there are deposits in which the upper layers of ore are brown iron ores, and the lower bedrock are siderites.

Figure 4 – Mineral siderite

Ilmenite – has the chemical composition FeTiO3 – iron salt of titanic acid. Ilmenite contains 36,8% iron and 31,8% titanium. It is always found in intergrowths with ordinary magnetite, i.e. as FeTiO3*Fe3O4. The ores formed by ilmenite are called titanomagnetites.

Figure 5 – General view of the mineral ilmenite

Titanium magnetite is a dense, difficult-to-reduce ore that produces thick and refractory titanium-containing slag. It has magnetic properties and is well enriched by magnetic separation. Often accompanied by vanadium.

Iron sulfide FeS2 in nature it is found in the form of the mineral pyrite or sulfur pyrite. It contains 46,6% iron. Iron ores do not form pyrite. It is used in the chemical industry, where it is burned to separate sulfur. Iron is oxidized and used in the form of pyrite cinders in the production of sinter.

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