question_answer

Discuss the occurrence of minerals and their formation. Give four points.

Answer:

(i) Minerals generally occur in igneous and metamorphic rocks. The smaller occurrences are called veins and larger are called lodes e.g. tin copper.

(ii) In sedimentary rocks they occur as layers or beds. Such as coal and petroleum. Some minerals like gypsum potash are formed as a result of evaporation.

(ii) Another type of formation involves the decomposition of surface rocks and the removal of soluble materials leaving the residual mass of weathered material containing ores  e.g. bauxite

(iv) Some minerals occur as alluvial deposits in sands of valiey floors and at the base of hills which are called as placer deposits. These are not corroded by water like gold silver etc.

(v) Ocean waters also contains some minerals like common salts magnesium bromine and manganese nodules.