What are Minerals? Mode of Occurrence of Minerals & Mineral Formation

A mineral is defined by geologists as a "homogeneous, naturally occurring substance with a definable internal structure." They are found in nature in a variety of forms, ranging from the hardest diamond to the softest talc. In our daily lives, we come into contact with a variety of metal-based objects. You've learned that the earth's crust is made up of various minerals embedded in rocks. Almost everything we use, from a tiny pin to a towering building or a big ship, all are made from it.

 

Minerals are usually found in �ores�. The term ore is used to describe an accumulation of any mineral mixed with other elements. The mineral content of the ore must be in sufficient concentration to make its extraction commercially viable. The type of formation or structure in which they are found determines the relative ease with which mineral ores may be mined.

 

This also determines the cost of extraction. It is, therefore, important for us to understand the main types of formations in which minerals occur.

 

Main Types of Formations are:

 

(i) In igneous and metamorphic rocks minerals may occur in the cracks, crevices, faults, or joints. The smaller occurrences are called veins and the larger is called lodes. In most cases, they are formed when minerals in liquid/ molten and gaseous forms are forced upward through cavities towards the earth�s surface. They cool and solidify as they rise. Major metallic minerals like tin, copper, zinc, and lead, etc. are obtained from veins and lodes.

 

(ii) In sedimentary rocks a number of minerals occur in beds or layers. They have been formed as a result of deposition, accumulation, and concentration in horizontal strata. Coal and some forms of iron ore have been concentrated as a result of long periods under great heat and pressure. Another group of sedimentary minerals includes gypsum, potash salt, and sodium salt. These are formed as a result of evaporation, especially in arid regions.

 

(iii) Another mode of formation involves the decomposition of surface rocks, and the removal of soluble constituents, leaving a residual mass of weathered material containing ores. Bauxite is formed this way.

 

Certain minerals may occur as alluvial deposits in sands of valley floors and the base of hills. These deposits are called �placer deposits� and generally contain minerals, which are not corroded by water. Gold, silver, tin, and platinum are the most important among such minerals.

 

(v) The ocean waters contain vast quantities of minerals, but most of these are too widely diffused to be of economic significance. However, common salt, magnesium, and bromine are largely derived from ocean waters. The ocean beds, too, are rich in manganese nodules.

India is fortunate to have fairly rich and varied mineral resources. However, these are unevenly distributed. Broadly speaking, peninsular rocks contain most of the reserves of coal, mica, and many other metallic and non-metallic minerals.

Sedimentary rocks on the western and eastern flanks of the peninsula, in Gujarat 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 north India are almost devoid of economic minerals. These variations exist largely because of the differences in the geological structure, processes, and time involved in the mineral formation.

 

Read More: Mineral in India: Classification Of Minerals- Ferrous & Non-Ferrous