Aluminium Minerals and Deposits

The most important row material of aluminium is bauxite; there are sedimentary rocks that consists a different compound of aluminium hydroxides which contain economically recoverable quantities of the aluminium mineral (45-60% Al₂O₃).The name derives from the description by Berther ,in 1821 ,of a sediment that occurred near the village of Les Baux in the Provence, France. Table 1 show the different type of bauxite minerals.

Table 1

Aluminium oxide,iron oxide and titanium and silicon dioxide are the major chemical components of all bauxites. Alkali and alkaline earth components are rarely found. For using bauxite in the industries. The bauxite must have a contain economically recoverable quantities and its SiO₂ contain must be less than 3-5 %.Table 2 shows principal chemical constituents of various bauxites%.

Deposit

Bauxite probably forms during long period of low geologic activity when the combination of high temperature, abundant precipitation, and good vertical drainage favors intensive chemical weathering. The sequence of leaching begins with removal of alkali followed by the removal of alkaline earths. Oxides of iron, aluminium, titanium and silicon are used and reprecipitated as hydroxides and oxides. Aluminium hydroxide and silica form kaolinite,Al₄(OH)₈Si₄O₁₀ Many of the geologically young bauxite deposits are located in the savannah region, which extends north and south of the tropical rain forest belt. The climate of this region is characterized by a high mean annual temperature and abundant precipitation during rainy season. Deposits occur on gently sloping hills or on peneplains.

Until the 1950s,The European aluminium industries was supplied from the karst bauxite deposits of France, Hungary, Yugoslavia, and Greece. United States Sources (Arkansas) and ore from Suriname provided the raw material for North American production. Today provided four countries, Australia, Guinea, Jamaica and Brazil more than half of the world's total bauxite output

Table2