Q. Describe about Halide Minerals?

Highly electropositive alkali and alkaline earth metals tend to form halide salts, which being soluble in water are washed away into the oceans due to leaching of the top soil. However, many deposits of halide minerals are also found under the soil. Some important halide minerals are rock salt (NaCl), sylvine (KCI), horn silver (AgCI), carnallite (KCl.MgC1₂.6H₂0), fluorspar (CaF₂) and cryolite (AlF₃.3NaF).

Ores as mined, generally contain variable amounts of unwanted minerals such as silica. clay, granite, etc. These unwanted materials are called gangue. The proportion of the desired metal in the ore must be sufficiently high so that the extraction of metal is chemically feasible and economically competitive. Ores of very low concentration are used only if they can be processed easily and inexpensively or if the metal produced is scarce. The lower limit of the percentage of the metal in mineral below which extraction becomes unprofitable depends on the value of the metal. Thus, ores containing 1 % tin are frequently worked upon to obtain tin and ores containing 5% tin are considered rich deposits of tin. If gold is present to the extent of even 0.0015%, it is considered worth extraction: On the other hand, iron and aluminium will not be worth extracting unless they contain 30% or more of the metal.