Mica

Topic: Mineral Resources of India: Distribution and Conservation · NCERT: Class 10, Ch 5 "Minerals and Energy Resources"; Class 12, Ch 5 "Mineral and Energy Resources"

Meaning

Mica is a non-metallic mineral (it has no metal to extract) made of thin plates, or leaves, that split into very thin, tough and flexible sheets. It matters because it insulates very well (it does not let electricity pass) and can bear high voltage. This makes it essential in the electrical and electronics industries.

Explanation

How mica forms

• Where it forms: mica is found in pegmatites. A pegmatite is a very coarse-grained igneous rock that forms in the last stage of magma cooling.
• Pegmatites are common in the old crystalline rocks of Peninsular India.

• → This is why mica comes from old plateau areas like the Chota Nagpur plateau, Nellore and the Aravalli region. The plains have none.

• Its structure: mica grows as flat layers stacked on top of each other. The layers separate easily.

• → So it peels into sheets so thin that a thousand sheets stacked together are only a few centimetres thick.

Why industry needs it

• High dielectric strength:
• Dielectric strength is how much voltage a material can take before electricity breaks through it.

• Mica's dielectric strength is very high.

• Low power loss: very little electrical energy is lost in it.

• Good insulation and resistance to high voltage.

• → So it is used in capacitors, insulators and heating elements.

• Remember: mica is useful because it blocks electricity, not because it carries it.

Types of mica in trade

• Sheet mica: large, whole sheets. This was the main export product. India once led the world sheet-mica trade.
• Scrap mica: small broken pieces. In Jharkhand these are often collected illegally.
• Why demand fell:
• Synthetic substitutes (factory-made materials) replaced natural sheet mica.
• → Demand for sheet mica fell, and the Indian trade declined.

Legal status

• Minor mineral since February 2015 [2].
• A minor mineral is one listed by the Centre. State governments make its rules and give its leases.
• → So mica producers now report production to the states, not to the Indian Bureau of Mines (IBM) [2].

Where it occurs

State	Belt / district	Key fact
Jharkhand (with Bihar)	Koderma–Gaya–Hazaribagh belt, lower Hazaribagh plateau, northern edge of the Chota Nagpur plateau	Leading producing belt. High quality. About 150 km long and 22 km wide
Andhra Pradesh	Nellore	Best-quality mica. Largest share of resources
Rajasthan	Belt of about 320 km from Jaipur to Bhilwara, and around Udaipur	NCERT Class 10 says "around Ajmer"
Minor producers	Telangana, Tamil Nadu, West Bengal (Purulia, Bankura), Madhya Pradesh, Karnataka (Mysuru, Hassan), Kerala (Alappuzha)	Small output

• Reserves (UNFC, as on 1 April 2015):
• UNFC (United Nations Framework Classification) is a standard way of grading how certain we are about a deposit.
• Total reserves and resources were 6,35,302 tonnes [2].
• Of this, 1,14,433 tonnes are "Reserves" and 5,20,869 tonnes are "Remaining Resources" [2].

• Andhra Pradesh leads with 41% of India's mica resources [2].

• Main mica-bearing pegmatites are in Andhra Pradesh, Bihar, Jharkhand, Maharashtra, Odisha, Rajasthan and Telangana [2].

• Problem areas: illegal scrap-mica collection in Koderma and Giridih (both in Jharkhand) has involved child labour.

Don't confuse with

• Metallic conductors (such as copper): copper is used in wires because it carries electricity. Mica is used because it blocks electricity and bears high voltage. Questions that call mica a "good conductor" are a trap.
• Largest producing belt vs largest resources vs best quality: Koderma–Gaya–Hazaribagh (Jharkhand) is the leading producing belt. Andhra Pradesh has the largest share of resources (41%) [2]. Nellore gives the best-quality mica.
• Limestone: both are non-metallic, but limestone is a sedimentary rock made of calcium carbonate and is used for cement and as a flux. Mica comes from igneous pegmatites and is used for electrical insulation.
• Major mineral: major minerals are regulated mainly by the Centre. Since 2015 mica is a minor mineral, so the states regulate it, just as they regulate river sand [2].

Prelims Hooks

• The Koderma–Gaya–Hazaribagh belt (Jharkhand/Bihar), in the lower Hazaribagh plateau, is the leading mica-producing belt. It is about 150 km × 22 km.
• Nellore (Andhra Pradesh) gives the best-quality mica. Andhra Pradesh also holds the largest share of mica resources (41%, 2015) [2].
• Rajasthan's mica belt runs about 320 km from Jaipur to Bhilwara, and is also found around Udaipur.
• Mica was declared a minor mineral in February 2015, so production is now reported to the states, not to the IBM [2].
• Mica occurs in pegmatites, coarse-grained igneous rocks that form when magma finishes cooling. It does not occur in sedimentary rocks.
• Trap: mica is valued for its high dielectric strength and insulation, not for conducting electricity.

Mains Points

• Geology decides location (GS-I): mica forms in pegmatites, which are found in the old crystalline rocks of Peninsular India. So it is concentrated in the Chota Nagpur plateau (Koderma–Gaya–Hazaribagh), Nellore and the Aravalli belt (Jaipur–Bhilwara–Udaipur). The Gangetic plains have none. This shows how rock type controls where minerals are found.
• Decline of the mica trade (GS-III):
• Synthetic substitutes cut world demand for natural sheet mica, so India lost its lead in the sheet-mica trade.
• Mica became a minor mineral in 2015, so control passed to the states [2].

• → Weak regulation allowed informal scrap-mica collection and child labour in Koderma and Giridih (Jharkhand).

• Way forward: build legal value chains with traceability (tracking each lot of mica from mine to buyer). Give mining families better livelihoods and schooling. Make state-level reporting and monitoring stronger now that the states regulate mica.

Related concepts

• Limestone
• Sand mining

Read more

• Non-metallic and rock minerals: mica, limestone and sand