You have studied that the earth’s crust is made up of different minerals embedded in the rocks. Minerals are a indispensable part of our lives. Almost everything we use from a tiny pin to a towering building or a big ship all are made from minerals.
Mineral is a “homogenous naturally occurring substance with a definable internal structure”.
Different modes of occurrence of minerals:
- IN IGNEOUS AND METAMORPHIC ROCKS
The minerals occur in the igneous or metamorphic rocks in cracks or faults.
The smaller occurrences are called veins and the larger occurrences are called lodes.
- IN SEDIMENTARY ROCKS
The minerals occur on beds or layers in sedimentary rocks, they are formed as a result of deposition and accumulation and concentration in horizontal strata.
Example: gypsum, potash salt, sodium salt.
- DECOMPOSITION OF SURFACE ROCKS
In this mode the minerals are formed by the decomposition of surface rocks, leaving a residual mass of weathered material.
- ALLUVIAL DEPOSITS
certain minerals occur as alluvial deposits in the sands of the valley.These deposits are called placer deposits.
Example: tin, gold, silver,etc.
- IN OCEAN WATER
ocean water contain a vast quantites of minearls but most of these are too widely diffused to be of economic significance.
Example: common salt, magnesium, etc.
Distribition of minerals in India:
- peninsular rocks contain most of the reserves of coal, metallic minerals, mica and many other non-metallic minerals.
- Sedimentary rocks on the western and eastern flanks of the peninsula in gujrat and assam have most of the petroleum deposits.
- Rajasthan with the rock systems of the peninsula, has reserves of many non-ferrous minerals.
- the vast alluvial plains of noth India are almost devoid of economic minerals.
Factors of viability of a reserve:
- concentration of mineral in the ore.
- the ease in extraction.
- closeness to the market.