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

Mineral deposits are the raw material base of industry and energy security; their classification and policy management therefore determine how effectively a country converts geology into development.

Genetic classification and concentration deposits. The modern classification of mineral deposits is genetic and hierarchical: endogenic deposits form within the crust and include magmatic, hydrothermal and metamorphic deposits; exogenic deposits form at or near the surface and include sedimentary, residual and mechanical deposits. Residual concentration deposits form when intense chemical weathering, especially in hot humid tropical climates, decomposes silicate rocks and removes silica, alkali and alkaline earth elements as soluble silica and clays, while less mobile metals such as iron, aluminium and nickel remain behind as oxides, hydroxides and silicates. The process is most effective where relief is low, drainage is slow, and the parent rock is rich in the metal; the result is a cap of ore over laterite. In India, residual deposits include lateritic nickel at Sukinda in Odisha, bauxite at Panchpatmali in Jharkhand, and iron ore in the Singhbhum region, where tropical weathering has concentrated iron oxides in lateritic caps. Mechanical concentration deposits, or placers, form when primary ore is eroded and transported by rivers, glaciers or waves; because heavy minerals have higher specific gravity than common sand and gravel, they settle first and become concentrated in favourable traps such as river bends, paleochannels, beach ridges or tidal flats. The mechanism is density sorting: as flow velocity decreases, heavy minerals drop out first, and repeated erosion and deposition increase grade. Indian examples include the monazite, ilmenite, rutile, zircon and cassiterite placers of the Kerala–Tamil Nadu coast, and alluvial gold in Jharkhand, where dense gold grains have been separated from lighter detritus by fluvial action.

National Mineral Policy and mineral categories. The premise of the National Mineral Policy 2019 is to ensure security of mineral supply for economic growth, defence and energy transition, while promoting sustainable mining, scientific exploration, private sector participation, efficient utilisation and minimal environmental impact. Within this framework, minerals are usefully distinguished as strategic, critical and essential. Strategic minerals are those vital for national security, advanced technology and emerging industries; they include rare earth elements, lithium and cobalt, with rare earth occurrences in the Chhattisgarh REE belts. Rare earth elements are used in magnets, defence electronics and clean-energy devices, while lithium and cobalt are needed for batteries. Critical minerals are indispensable for manufacturing, infrastructure and clean energy but carry higher supply risk; examples are copper at Malanjkhand in Chhattisgarh, tungsten in Kerala, and molybdenum at Degana in Rajasthan. Essential minerals are bulk minerals required for basic industry and everyday life; iron ore, manganese, bauxite and coal are typical, occurring in the Odisha–Jharkhand–Chhattisgarh belt and other major sedimentary and igneous provinces.

Manganese deposits of India. Manganese in India occurs mainly as bedded or stratiform deposits in the Dharwar Supergroup and associated iron formations, indicating a syngenetic sedimentary origin with later supergene enrichment. The deposits are typically banded, with manganese oxides and carbonates interbedded with iron-rich shales and cherts; supergene enrichment increases manganese dioxide in oxidised zones. The largest and highest-grade deposits are in Balaghat, Madhya Pradesh, while other important districts are Nagpur–Bhandara in Maharashtra, Keonjhar and Sundergarh in Odisha, Dharwar in Karnataka and Vizianagaram in Andhra Pradesh. Manganese is used chiefly in ferromanganese for steelmaking, where it acts as a deoxidiser and controls sulphur, and also in dry-cell batteries, chemical industry and aluminium alloying. Although India has the seventh largest global manganese reserves and is a major producer, it still imports battery-grade and high-purity manganese, showing that mineral security depends not only on quantity but on grade, processing and policy support.