(a) Give the modern classification of mineral deposits and explain in brief the residual and mechanical concentration deposits…

(a) Classification of mineral deposits; residual and mechanical concentration

The modern classification is genetic. Endogenic deposits form within the Earth: magmatic (chromite, PGE, diamonds in kimberlite), hydrothermal (gold, base-metal sulphides) and metamorphic (graphite, garnet). Exogenic deposits form at or near the surface: sedimentary (banded iron formations, evaporites, coal), residual and mechanical concentrations, and supergene enrichment deposits.

Residual concentration: intense chemical weathering in warm, humid climates with low relief and slow drainage leaches soluble silica, alkalis and alkaline earths from the parent rock, leaving insoluble elements enriched in place as a laterite cap. Bauxite forms over aluminous rocks, as at Panchpatmali in Koraput, Odisha, and on the Eastern Ghats and Western Ghats plateaus; nickel laterite forms over ultramafic rock, as in the Sukinda valley, Odisha; weathering also enriches manganese and iron ores.

Mechanical concentration (placers): weathering liberates durable, dense minerals which are sorted by running water or waves. Heavy grains settle first where velocity drops, in river bends, palaeochannels, beach ridges and bars. Required traits are high specific gravity, hardness and chemical stability. Indian examples are the monazite, ilmenite, rutile, zircon and garnet beach-sand placers of the Kerala, Tamil Nadu and Odisha coasts, and alluvial gold along rivers of Jharkhand such as the Subarnarekha.

(b) National Mineral Policy and strategic, critical and essential minerals

The premise of the National Mineral Policy 2019 is that minerals are a finite, valuable natural resource and the raw material of industry, so their exploration and extraction must serve national growth, supply security and defence needs while being sustainable, transparent and environmentally sound, with greater private investment and better exploration.

Strategic minerals are those whose supply is vital for defence, nuclear and advanced technology; examples are rare earth elements, available as monazite sands on the Kerala and Odisha coasts, and uranium. Critical minerals are essential for the economy, clean energy and manufacturing but carry supply risk, mostly import dependence; the Ministry of Mines listed 30 in 2023, including lithium (Mandya in Karnataka and Reasi in Jammu and Kashmir), cobalt, nickel, graphite and tungsten (Degana in Rajasthan). Essential or bulk minerals are the high-volume base of industry and infrastructure, as iron ore in Odisha, Jharkhand and Chhattisgarh, bauxite, manganese, coal and limestone.

(c) Manganese deposits of India

Mode of occurrence: bedded, metamorphosed Precambrian sedimentary deposits. Gondite deposits of the Sausar Group, in Balaghat and Chhindwara in Madhya Pradesh and Nagpur and Bhandara in Maharashtra, and Kodurite deposits, in Srikakulam and Visakhapatnam in Andhra Pradesh and Ganjam and Koraput in Odisha, are metamorphosed. Others are bedded lenses within the Iron Ore Group of Odisha (Keonjhar, Sundargarh) and the Sandur belt of Karnataka, often enriched by weathering.

Distribution: Odisha holds about 44% of resources, Karnataka about 22% and Madhya Pradesh about 12%, then Maharashtra and Goa.

Uses: 90–95% goes into iron and steel as ferromanganese and silicomanganese, as deoxidiser, desulphuriser and alloy; the rest goes into dry-cell batteries, chemicals and glass.