Chromium ore: composition, deposits and applications. Chrome metal features

2024 Author: Howard Calhoun | [email protected]. Last modified: 2023-12-17 10:16

Hard and refractory metal chromium is in great demand in many industries. It is used to make dyes, stable alloys and coatings for various surfaces, as well as refractory materials. In nature, it exists in the form of numerous compounds in the composition of rocks and minerals. This article talks about chromium ore, its deposits and mining methods.

24th element

Chromium is an element of the sixth group of the periodic table with atomic number 24. As a simple substance, it is one of the hardest metals, but this quality is highly dependent on its purity. With various impurities, its hardness increases, but in its pure form, chromium can be quite ductile.

The melting point of the metal is above 1800 degrees Celsius and also depends on the amount of impurities. Due to its infusibility, it becomes active only when heated, and under normal room conditions, it remains inert. So, it reacts with water, onlybeing very red-hot and ground into powder. In its normal state, it is not active with air, sulfuric and nitric acids. Faced with them, it passivates, forming a thin protective film that does not allow it to enter into a further reaction. However, when heated, it easily dissolves in acids, and at temperatures above 600 degrees, it burns in oxygen.

In its normal state, chromium is a metal with a pronounced white-blue tint. Oxidized to degrees +2, +3 and +6, it forms a huge number of compounds that can be red, green, blue, orange and even yellow. Because of this, he was nicknamed "chromium", which means "color" in Greek.

Chromium ore

Chromium is widely distributed on planet Earth - its content in the earth's crust is 0.012% by weight. It does not form nuggets and does not occur on its own. In nature, it exists only in compounds of various minerals, for example, in wokelenite, ditzeite, uvarovite, crocoite, melanchroite. Usually they are dark, almost black in color and have a characteristic metallic sheen.

Chrome ores form minerals that belong to the group of chrome spinels. It is they that contain the largest amount of metal, sufficient for its industrial use. They include four main raw materials:

• aluminochromite;
• birch (magnochromite);
• picotite;
• chromite.

Ore minerals are of igneous origin. They vary greatly in composition, but are very similar in appearance and structure. Each other. They can only be distinguished by chemical analysis.

Chrome spinels are distinguished by high hardness, black, brown-black and gray color, weak magnetic properties. They are often accompanied by uvarovite, olivine, brucite, serpentine, kemmererite, and bronzite. The main source of the metal is chromite.

Deposits

Deposits of chrome ores exist on the territory of Eurasia, Africa, as well as South and North America. South Africa has the largest reserves, accounting for more than 75% of the total explored volume of chromium. After it, Kazakhstan and Zimbabwe lead in terms of ore reserves, followed by the USA, India, Oman, Turkey.

Large deposits are also concentrated in Russia, where they are present mainly in the Urals. At the beginning of the 19th century, Russian chrome ores were the main source of metal in the world, but the emphasis shifted with the discovery of other deposits. Today, the country's consumption of this resource exceeds its production.

Ore, as a rule, lies at considerable depths, therefore it is extracted from the bowels of the planet mainly by the mine method. In 10-15% of cases, mining occurs with the help of quarries. About 15 billion tons of ore are extracted annually.

Use

In industry, the main value of the metal is that it is very resistant to corrosion and does not collapse under the influence of air and water. These properties are used to produce stainless steels, which are characterized by high strength and hardness. Refined chrome is also coated on aluminum, magnesium, silver, zinc, cadmium and some other metals to protect them from environmental influences.

Chromium ores, containing less chromium but rich in magnesium and aluminum oxides, are used to produce refractory materials that can withstand high melting temperatures.

Its colored compounds are used to create dyes, pigments and colored glasses. Synthetic rubies are made from alloyed trivalent chromium and molten corundum mineral, which are used in jewelry.