Geology help???

Question

hi

can some one explain the formation of bauxite? and its economical metal??

i know it cause of chemical leaching, but i'm unsure how to explain it , and unsure about the economical metal?

thanks

Answer 1

Basically, bauxite forms in three steps:

(1) desilication, in which silica is removed from clays, from feldspars, and from other aluminous minerals

(2) migration, in which clay minerals and hydrous aluminum oxides are transported within the deposit from the place where they were formed to their present position

(3) resilication, in which silica is added to gibbsite to form a hydrous aluminum silicate or clay.

Aluminum can be extracted from bauxite; however, recycling of old aluminum is more economical.  That being said, bauxite is still mined for aluminum.  Of all bauxite mined about 85% is converted into aluminum.

Answer 2

Lateritic bauxites (silicate bauxites) are distinguished from karst bauxites (carbonate bauxites). The early discovered carbonate bauxites occur predominantly in Europe and Jamaica above carbonate rocks (limestone and dolomite), where they were formed by lateritic weathering and residual accumulation of intercalated clays or of clayey dissolution residues of the limestone.

The lateritic bauxites occur in many countries of the tropical belt. They were formed by lateritization (see laterite) of various silicate rocks such as granite, gneiss, basalt, syenite and shale. Compared with iron-rich laterites, the formation of bauxites demands even more intense weathering conditions with a very good drainage. This enables dissolution of kaolinite and precipitation of gibbsite. Zones with highest aluminium content are frequently located below a ferruginous surface layer. The aluminium hydroxide in the lateritic bauxite deposits is almost exclusively gibbsite.