Metals Found in Native Form in India: Distribution and Major Deposits

Native metals occur in nature in a pure, uncombined metallic state without bonding with other chemical elements. Most metals form oxides, sulfides, or carbonates due to reactivity with oxygen and sulfur. In India, unreactive metals like gold, silver, copper, and platinum group elements occur in their native elemental form within placer deposits and hydrothermal veins.

Geological Occurrence of Native Metals

Native elements belong to a distinct mineral class characterized by metallic bonding and high electrical conductivity. These metals resist chemical weathering, allowing them to survive transport in river systems.

Primary Hydrothermal Veins

• Hydrothermal fluids deposit pure metals inside quartz veins along shear zones and faults.
• Gold and native silver precipitate alongside sulfide minerals like pyrite, arsenopyrite, and chalcopyrite.
• The Dharwar Craton and Singhbhum Shear Zone host primary auriferous quartz reefs.

Secondary Placer and Alluvial Deposits

• Weathering breaks down metal-bearing parent rocks over geological epochs.
• Dense native metals accumulate in river gravels, paleochannels, and beach sands as heavy minerals.
• Placer gold, native platinum, and osmiridium occur as grains, dust, and nuggets in fluvial beds.

Native Gold Distribution in India

Gold is the most widespread native metal found in India, occurring in both lode deposits and alluvial placers.

Primary Lode Gold Deposits

• Karnataka: The Kolar Gold Fields in Kolar district contain gold in quartz veins hosted within Archaean metavolcanic rocks. The Hutti Gold Mines in Raichur district host primary auriferous quartz-carbonate veins and remain India’s primary operational gold producer.
• Andhra Pradesh: The Ramagiri Gold Field in Anantapur district and the Bhadrampalle zone contain native gold in schistose formations. The Jonnagiri belt in Kurnool district hosts sheared granodiorite formations with free gold grains.
• Jharkhand: The Kundarkocha and Lawa deposits in East Singhbhum district contain native gold associated with quartz veins in the Singhbhum Shear Zone.
• Rajasthan: The Bhukia-Jagpura belt in Banswara district holds native gold intergrown with copper and cobalt sulfide minerals.

Alluvial and Placer Gold Deposits

• Subarnarekha River Basin: The river flows through Jharkhand, West Bengal, and Odisha, carrying alluvial gold flakes extracted by local communities.
• Kerala: The Nilambur valley in Malappuram district contains placer gold deposits in the Chaliyar and Punnapuzha river basins.
• Assam and Arunachal Pradesh: Rivers like the Subansiri, Brahmaputra, and Noa-Dihing contain auriferous gravels derived from the Higher Himalayas.
• Jammu and Kashmir: The Indus River gravels near Kargil, Dras, and Leh contain detrital native gold grains.

Native Copper Occurrences

While most copper occurs as chalcopyrite, bornite, and malachite, elemental copper occurs in oxidation zones and basalt cavities.

Major Native Copper Zones

• Deccan Traps: Secondary native copper fills vesicular cavities and amygdales in basalts across Kolhapur and Satara in Maharashtra.
• Khetri Copper Belt: Sikar and Jhunjhunu districts of Rajasthan show minor occurrences of dendritic native copper in the supergene enrichment zones of copper lodes.
• Singhbhum Copper Belt: Mosabani, Rakha, and Surda mines in Jharkhand contain traces of wire-shaped native copper.
• Andhra Pradesh: The Agnigundala belt in Guntur district hosts occasional native copper sheets within quartzites and phyllites.

Native Silver and Platinum Group Elements (PGE)

Native silver and platinum group elements occur in restricted geological settings within India.

Platinum Group Elements in Layered Complexes

• The Sittampundi Anorthosite Complex in Namakkal district of Tamil Nadu contains native platinum and palladium alloys.
• The Baula-Nausahi igneous complex in Keonjhar district of Odisha hosts PGE mineralisation within brecciated chromitite zones.
• The Hanumalapura area in the Shimoga schist belt of Karnataka contains native platinum disseminations in titaniferous magnetite bands.

Extractive Methods for Native Metals

Indigenous and industrial methods separate native metals based on their high specific gravity and chemical inertness.

Gravity Separation

• Panning and sluicing separate heavy native metal grains from river sand and gravel matrices.
• Industrial shaking tables and spiral concentrators recover liberated metal particles from crushed ore without chemical reagents.

Froth Flotation and Amalgamation

• Modern mineral beneficiation routes float sulfide minerals and free metal grains using collector reagents.
• Historical amalgamation used liquid mercury to dissolve native gold, though modern operations use carbon-in-leach cyanidation for extraction.

Facts on Native Metals in India

• The word Subarnarekha translates literally to “Streak of Gold” due to its rich history of alluvial gold panning.
• The Kolar Gold Field was one of the deepest gold mines in the world, reaching depths of over 3,000 meters before closing in 2001.
• Native gold has a specific gravity of 19.3, making it nearly twenty times heavier than water and easy to recover by panning.
• Electrum is a natural alloy of native gold with more than 20 percent native silver found in Indian lode deposits.
• Native copper found in Deccan Traps was historically collected by local artisans to make utensils and decorative ornaments.
• The Geological Survey of India identified the Hanumalapura belt in Karnataka as a potential source for commercial native platinum exploration.
• The Nilambur river bed in Kerala contains gold grains originating from the weathered quartz veins of the Wayanad plateau.
• Native iron of terrestrial origin is extremely rare and only occurs where magma encounters carbonaceous sediments or under deep mantle reduction conditions.
• Most of India’s current domestic gold extraction takes place at the Hutti mine in Raichur, Karnataka, managed by the Hutti Gold Mines Limited.