Minerals are defined as naturally occurring homogeneous substances that have a definite internal structure. Some minerals are essential for our body to carry out its chemical and biological processes. A rock may contain one or several types of minerals mixed with organic material.
A geographer studies about the distribution and economic importance of a mineral while, a geologist studies the formation, age and composition of minerals. The properties of a mineral depend on the elements it is made of, and the chemical and physical conditions in which it was formed.
Minerals are classified as metallic minerals, non-metallic minerals and energy or fuel minerals. The metallic minerals can be further classified as ferrous minerals, or the ones that contain iron, non-ferrous minerals and precious metals, like gold, silver and platinum.
Minerals occur in the earth’s crust as:
- Veins and lodes in igneous and metamorphic rocks
- Beds or layers in sedimentary rocks
- Alluvial or placer deposits on valley floors
- Residual mass after weathering of surrounding rocks
Some metallic minerals, like gold, silver, platinum and tin, are found as alluvial deposits in the sand and soil in valleys. Such alluvial deposits are also called placer deposits. Around 70% of the surface of the earth is covered by water. The water of the seas and oceans, and the ocean floors, also have rich mineral deposits.
India has rich mineral resources in some parts of its territory. To be an ore, a mineral should:
- Be abundantly available
- Offer sufficient concentration of an element
- Have a commercially viable process of extraction
The places from where mineral ores are extracted are called mines. All the mineral reserves in India are owned by the government. In Meghalaya, families lay claim to coal deposits, and mine coal by digging long narrow tunnels in the ground. This practice is called rat hole mining.