Have you ever encountered an unusual โclayโ that for some reason did not form a mass suitable for sculpting with water? If so, then you did not hold clay in your hands, but bauxite rock. Its formula cannot reflect the exact composition, because a variety of substances are able to enter it. But first things first. Consider this rock in all angles, having studied in detail the composition, properties and significance for humans.
History of discovery and why it is called
The name of the ore is the same as the place of its discovery. The composition is very diverse, but the main components are different hydrates of aluminum oxides, iron-containing and silicon-containing substances. The chemical formula of bauxite does not reflect the entire composition, but it is used mainly in the aluminum industry as the main source of raw materials. The content of aluminum-containing substances can be 40-60% or more.
A dense mineral comes in many different shades: from red to green and gray. But you will never meet transparent bauxite. More often - dense and solid, sometimes it occurs in the form of earthy and loose substance. In this case, traces will remain on the hands when touched.
Perhaps we would now call this mineral burtite if, in 1821, a French geologist named Pierre Berthier did not become modest if he found an unusual find during his summer vacation. The rock discovered by him was made of stone with unusual properties.
Berthier did not know that several decades would pass, and bauxite, whose formula is Al 2 O 3 xnH 2 O, would become the raw material without which the aluminum industry did not develop at such a fast pace. But what happened is what happened. And the mineral is called the Provence village of Le Beaux de Provence (written in French Les Baux).
It took 30 years for the composition of the rock to be evaluated by the mineralogists of the time, but in the 50s bauxite took its place in the Paris exhibition center, originally called "clay silver". It looks very much like clay.
Composition
In order for the formula of bauxite in chemistry to accurately reflect the composition of the mineral, it is necessary to take into account all the substances that enter it. There are many of them, let's call those that are found most often:
- hydrates of aluminum oxides, you are already familiar with it - Al 2 O 3 xnH 2 O;
- ore-forming hydroxides, oxides and silicates of iron;
- silicon (quartz (SiO 2 ), opal (SiO 2 x nH 2 O), kaolinite (Al 4 [Si 4 O 10 ] (OH) 8 ));
- titanium (rutile (TiO 2 ) and others);
- carbonates (CaCO 3 , MgCO 3 , etc.);
- compounds of chromium, zirconium, phosphorus, sodium, potassium, vanadium, gallium and other elements;
- pyrite (FeS 2 ).
Ore, primarily containing alumina, is valued, and silica the less the better. To characterize the quality, the so-called silicon module of bauxite was introduced, its formula for finding: ฮผ Si = Al 2 O 3 / SiO 2 . The obtained value shows which of the methods to process ore better.
The properties
As already mentioned, the composition of the mineral is very diverse, which greatly affects its properties. But some physical properties can be distinguished:
- colors - you can find all shades of red (from light pink to dark red), green (from gray-green to grassy) and gray (from light colors, including white to dark gray almost black);
- the state can also be different: they produce stony, porous, loose, earthy and clay-like;
- the density directly depends on the amount of iron-containing substances and varies from 1.8 to 3.2 g / cm 3 ;
- hardness is maximum 6 on the Mohs scale;
- opaque.
For industry, there is one chemical feature that is most important is โopenabilityโ, which means whether it is easy to extract aluminum oxides from this ore.
Places where there are deposits
Bauxite is mined either open pit or underground. The main ore reserves are concentrated where humid and warm are the tropics and subtropics. Here are the best bauxite deposits and 2/3 of the world's reserves.
If we are talking about the Russian Federation, then its deposits are not enough even to ensure their own needs. But development is underway. Bauxite ore is mined in the Arkhangelsk, Leningrad and Belgorod regions, Sverdlovsk and Chelyabinsk.
A constant increase in demand for aluminum leads to an increase in production. The United States has calculated that global bauxite reserves are between 55 and 75 billion tons. This is enough for about a hundred years. What's next? Scientists are trying to find other ways to extract aluminum, just as effective and cheap.
Recycling
Aluminum is the main reason for the extraction of this ore. The process of extracting it consists of the following steps: obtaining alumina, then pure metal (by electrolysis). Alumina (alumina formula), in turn, can be obtained by the Bayer method, sintering or a combined method.
The Bayer process scheme is as follows: the highly ground bauxite is treated with sodium hydroxide to obtain sodium aluminate, from which alumina is then precipitated. All that remains is to carry out electrolysis - and aluminum is ready.
Low-grade ore is sintered. This process is as follows: the crushed rock is mixed with calcium carbonate and soda, placed in an oven and sintered at 1250 ยฐ C. Then the cake is treated with low concentration sodium alkali, aluminum hydroxide is filtered and electrolysis is carried out.
The combined method consists of the primary processing of alumina from bauxite by the Bayer method and the subsequent processing of the remaining helmet by sintering.
Application
Having studied bauxite, its properties and applications in metallurgy, it is now possible to find out where ore is still used. In the chemical industry in the manufacture of paints, as a filler in the composition of varnishes. As a sorbent it is used by the oil refining industry.
Iron and steel industry uses fluxes obtained by smelting the rock. And electrocorundum obtained in an electric furnace from bauxite, having a hardness of 9 on the Mohs scale, is used in the form of abrasive material.
Another component of bauxite is used - alumina. Alumina cement is produced from it - a composition that has high astringent properties even at low temperatures, which is especially important for housing construction in the Far North.
If bauxite, the formula and application of which we are now considering, contains a small amount of iron, then the rock is used in the manufacture of refractories.
But for lithotherapists and magicians, bauxites are of no interest, since the rock does not have either healing or magical properties.
Occasionally, only jewelers can have fun creating some trinket or souvenir from ore, for example, polishing them in the shape of a ball - and onto a stand.
It looks impressive and original.