Name: Probably used in the mineralogical sense by 1706 and originally "smicka" and from the Latin micare - to flash or glisten in allusion to the material's appearance. Isinglass predates the use of mica as a mineral term and known from at least 1535, but isinglass also referred to the matter from the sturgeon fish that also had pearly flakes from the scales. Mica is widely distributed and occurs in igneous, metamorphic and sedimentary regimes. Mica group represents 34 phyllosilicate minerals that exhibits a layered or platy structure. Commercially important mica minerals are muscovite (potash or white mica) and phlogopite (magnesium or amber mica). Granitic pegmatites are the source of muscovite sheet, while phlogopite is found in areas of metamorphosed sedimentary rocks into which pegmatite rich granite rocks have been intruded. It possesses highly perfect basal cleavage due to which it can easily and accurately split into very thin sheets or films of any specified thickness. It has a unique combination of elasticity, toughness, flexibility and transparency. It possesses resistance to heat and sudden change in temperature and high dielectric strength. It is chemically inert, stable and does not absorb water.

1. ❖ Introduction
Name: Probably used in the mineralogical sense by 1706 and originally "smicka" and from the Latin micare - to flash
or glisten in allusion to the material's appearance. Isinglass predates the use of mica as a mineral term and known from
at least 1535, but isinglass also referred to the matter from the sturgeon fish that also had pearly flakes from the scales.
Mica is widely distributed and occurs in igneous, metamorphic and sedimentary regimes. Mica group represents 34
phyllosilicate minerals that exhibits a layered or platy structure. Commercially important mica minerals are muscovite
(potash or white mica) and phlogopite (magnesium or amber mica). Granitic pegmatites are the source of muscovite sheet,
while phlogopite is found in areas of metamorphosed sedimentary rocks into which pegmatite rich granite rocks have
been intruded. It possesses highly perfect basal cleavage due to which it can easily and accurately split into very thin
sheets or films of any specified thickness. It has a unique combination of elasticity, toughness, flexibility and transparency.
It possesses resistance to heat and sudden change in temperature and high dielectric strength. It is chemically inert, stable
and does not absorb water.
❖ Chief mica minerals
1. Muscovite - Potassium mica (White, ruby mica)
2. Paragonite - Sodium mica
3. Phlogopite - Magnesium mica (Amber Mica)
4. Biotite - Magnesium-Iron Mica (Black mica)
5. Lepidolite - Lithium mica
6. Zinnwaldite - Lithium-Iron mica (Lithium biotite)
7. Roscoelite - Vanadium mica
❖ Properties of Mica
Mica belongs to a very important and rather large group of minerals that are highly suitable for several applications.
However, its advanced properties make it highly suitable for use in various places. These are:
• Physical: Mica is translucent, easily split into thin films along its cleavage, optically flat, colorless in thin sheets,
elastic and incompressible.
• Chemical: It is a compound hydrous silicate of aluminium, which also contains iron, magnesium, potassium,
sodium fluorine, lithium and also few traces of numerous other elements. It is constant and entirely static to the
action of water, acids (except for hydrofluoric and concentrated sulphur), alkalies, conventional solvents, bases,
and oil. It remains almost unchanged by atmospheric action.
• Electrical: Mica has the exclusive combination of uniform dielectric steadiness, capacitance stability, enormous
dielectric power, high Q factor and lower power loss, high electrical resistance and low temperature coefficient.
It is highly regarded for its resistances to arc and corona discharge without causing any lasting injury.
• Thermal: It is highly fire proof, incombustible, non- flammable, infusible, and also can resist temperatures of up
to 1000 degrees Celsius/1832 degrees Fahrenheit. However this depends on the type and variety of Mica used. It
has excellent thermal stability, lower heat conductivity, and can be easily exposed to high temperatures without
visible effect.
• Mechanical: Mica is highly tough, having high tensile strength, elastic, and along with being flexible. It has
immense compression power and can be machined, die-punched, or hand cut.
❖ Mode of Occurrence and Origin
Muscovite occurs in silicic pegmatites, mostly in association with granitic intrusive. Phlogopite comes from
quartz-free pegmatites. Biotite is obtained from metamorphic rocks-biotite-schists. Lepidolite and zinnwaldite are
restricted to granitic pegmatites in some areas. micas, as a whole, occur as a constituent of pegmatites and veins which
penetrate the mica-schists. Commercial micas occur as zonally distributed 'books' in the pegmatites. The mica books vary
in size considerably even within the short distances within the pegmatite bodies. Single books of muscovite weighing half
a tonne have been mined in the Bihar mica-belt.
The pegmatites are composed normally of plagioclase felspar and quartz, but also, in places, contain orthoclase
felspar and such minerals as tourmaline, garnet, apatite and very rarely beryl. They have been emplaced along favourable
structures such as noses and limbs of folds, bedding, foliation, slip planes and joints, and are commonly long, narrow,
lensoidal and, in places, arcuate and sinuous. They vary in size from insignificant stringers to big bodies, 500 m long and
30 m wide. Petrographically, distinct mappable units exist in a zoned or composite pegmatite with a central quartz core,
followed by a zone of pegmatite with quartz, felspar and mica, and a mica zone at the contact of the pegmatite-vein and
the country rock.
GL-Apr-2018 last update – June-19 Economic Geology
Q U A R T Z – E C I E S Nikhil V. Sherekar
Mica
NikhilV.Sherekar8390377801(M.Sc.GeologyGATE+SET+NET-CSIR-UGC-JRF-AIR28)

2. The mica has been formed from magmatic solutions in the pegmatite. It may be an igneo-aqueous deposit or
hydrothermal replacement of earlier minerals. It has been observed that pegmatites occurring within mica-schists are
richer in mica books compared to those occurring within other rock types. It is, hence, reasonable to assume that the
country rock-mica-schist has contributed, in part, towards the formation of mica. The fluids responsible for the formation
of mica-pegmatite, were rich in volatiles (H20, F, B etc.) and (K, Na, Li, Al and Si). The intrusive origin of mica-
pegmatites is agreed upon by most Indian workers. These mica-pegmatites may have formed at a high temperature below
a great thickness of the crust which has since been removed. It has been suggested that the formation of pegmatites is
favoured in a geological setting where the mica-schist, country rock, has metamorphosed under Amphibolite-facies
conditions. The origin of phlogopite mica is different from that of muscovite where the former forms under the action of
gases, vapours and aqueous solutions of granitic magma on magnesium rich host rocks, dolomitised limestones and
dolomites. Under the action of magma pure limestone re-crystallised into to marble, and dolomitised •limestones turn into
diopside rocks.
The main source of commercial mica is the pegmatites which occur Within the metamorphic rocks, such as schists
and gneisses of Archaean age. The pegmatites are the intrusive igneous bodies which are formed from the late residual
magma. The magma which is left in the last stage of crystallization is called "late residual magma". This magma mostly
contains alkalies, water, carbon dioxide and rare elements.
❖ Distribution
World's best quality of mica comes from India and the workable deposits have been recorded mainly from Bihar,
Andhra Pradesh and Rajasthan. The occurrences of less significance are noted in the states of Tamil Nadu,
Karnataka, Kerala, West Bengal, Madhya Pradesh and Orissa.
In India, deposits of mica occur in three important belts: (i) mica belt of Bihar, (ii) mica belt of Andhra Pradesh,
and (iii) mica belt of Rajasthan.
▪ Mica Belt of Bihar. This belt extends in the ENE-WSW direction for a distance of about 150 km. Its width
is about 20 km. This mica belt starts from Gaya district in the west and runs through Hazaribagh and Mongyr
districts to Bhagalpur district in the east. The country rocks are mainly mica-schists of Archaean age. These
rocks have been intruded by dykes of metadolerite and pegmatites. Bihar mica belt contains mica of ruby-red
colour. The commercial deposits of mica are found in those pegmatites which occur within micaschists and
mica-gneisses. There are about 600 mines in this belt. The mining activities are mainly centred in the Kodagna
area of Hazaribagh district.
▪ Mica Belt of Andhra Pradesh. In Andhra Pradesh, the mica is obtained chiefly from the "Nellore-mica-belt'".
This belt 'is about 96 km long and 16 km wide. It extends in the NW-SE direction between Gudur and Sangam.
The host rocks are mica-schists, chlorite-schists and hornblende-gneisses of Archaean age. These rocks contain
sheets, lenses and masses of pegmatite which contain mica. The common Nellore-mica is of green colour.
▪ Mica Belt of Rajasthan. In Rajasthan, deposits of mica are found in Ajmer-Merwara, Mewar, Jaipur and
Bhilwara districts. The mica pegmatites occur as intrusive in the gneisses and schists of Archaean age. The
quality of mica is of the ruby-red type but green mica is also produced in small quantity.
Geological Distribution of Mica in India
Formation Area Geological Details
Precambrian, predominantly mica-schist
besides ca}c-granulite and gneisses,
homblendeschist, micaceous quartzite
and conglomerate (955 ± 40 million
years)
Bihar Mica Belt
Bihar Mica- The mica-pegmatites are
localised mainly in mica-schist and
micacious quartzite, and rarely in
hornblende-schist
Biotite-schist and hornblendeschist
interbanded with minor quartzite,
felspathic-schist etc.
(1570 million years)
Nellore Mica Belt
Mica-bearing pegmatites are most fre- quent
(70%) in biotite-schist and other rocks.
Pre- Vindhyan metasediment intruded by
granites of different ages
Rajasthan Mica Belt The pegmatites carrying mica are commonly
intrusive into steeply deeping muscovite-
biotite-schist, micaceous quartzite and less
commonly into amphibolite, dolerite and calc-
silicate rocks.
Archaean gneisses
Nilgiri Tamilnadu
The pegmatites carrying muscovite are
intrusive into gneisses
NikhilV.Sherekar8390377801(M.Sc.GeologyGATE+SET+NET-CSIR-UGC-JRF-AIR28)

3. Charnokite and Leptynite
MAdugula,
Tamilnadu
Irregular pockets ofphlogopite are formed at
the contact of pegmatites with chamockite and
leptynite. The deposits are not of much
significance
Peninsular Gneissic complex
Mysore and Hassan
Distt. Karnataka
The distribution of mica in pegmatites is very
erratic
Calc-gneiss, dunite and norite
Neyoor and Punaloor,
Kerala
Phlogopite mica is concentrated at the contact
of pegmatite with calc-gneiss and dunite
Gneisses and Schist Bankura and Purulia
dist. West bengal
Occurrences of muscovite of not much
economic significance have been noted,
❖ Geographical Distribution of mica in India
India is a major producer of Mica in the world. It is the largest producer of sheet mica. According to British Geological
Survey, the world’s largest deposit of mica is at Koderma district in the state of Jharkhand (India). About 95% of India’s
mica is distributed in just three states of Jharkhand, Andhra Pradesh and Rajasthan.
1. Jharkhand: Jharkhand has richest mica belt and accounts for 60% of India’s production in terms of value.
Here, mica is found in a belt extending for about 150 km in length and 32 km in width from Gaya district
of Bihar to Hazaribagh and Koderma districts of Jharkhand. Koderma is a well-known place for mica
production in Jharkhand which produces more than 50% of the total mica production in India.
2. Andhra Pradesh: This is the second largest producer and accounts for nearly 25% of India’s mica. The
main belt lies in Nellore district and is 97 kms long and 24-30 km wide.
3. Rajasthan: The main mica-bearing belt of Rajasthan extends from Jaipur to Udaipur. This is 322 km long with
an average width of 96 km. This is quite wide in its middle part near Bhilwara. The main mica-producing districts are
Bhilwara, Jaipur, Tonk, Sikar, Dungarpur and Ajmer.
4. Other Producers: Some mica is produced in Maharashtra, Karnataka, Kerala, Tamil Nadu, Orissa, Madhya
Pradesh, West Bengal, Haryana and Himachal Pradesh. These areas account for just 1% mica production of India.
❖ These are the Mica Group Members:
The True Micas:
Dioctahedral:
o Aluminoceladonite (Potassium Aluminum Magnesium Iron Silicate Hydroxide)
o Boromuscovite (Potassium Boro-silicate Hydroxide)
o Celadonite (Potassium Iron Magnesium Silicate Hydroxide)
o Chromphyllite (Potassium Chromium Aluminum Silicate Hydroxide Fluoride)
o Ferro-aluminoceladonite (Potassium Aluminum Iron Magnesium Silicate Hydroxide)
o Ferroceladonite (Potassium Iron Magnesium Silicate Hydroxide)
o Muscovite (Potassium Aluminum Silicate Hydroxide) Variety: Fuchsite
o Nanpingite (Cesium Aluminum Silicate Hydroxide)
o Paragonite (Sodium Aluminum Silicate Hydroxide)
o Roscoelite (Potassium Vanadium Aluminum Silicate Hydroxide)
o Tobelite (Ammonium Aluminum Silicate Hydroxide)
Trioctahedral:
o Annite (Potassium Iron Aluminum Silicate Hydroxide)
o Aspidolite (Sodium Magnesium Aluminum Silicate Hydroxide)
o Biotite (Potassium Magnesium Iron Aluminum Silicate Hydroxide Fluoride)
o Eastonite (Potassium Magnesium Aluminum Silicate Hydroxide)
o Ephesite (Sodium Lithium Aluminum Silicate Hydroxide)
o Hendricksite (Potassium Zinc Aluminum Silicate Hydroxide)
o Lepidolite (Potassium Lithium Aluminum Silicate Fluoride Hydroxide)
o Masutomilite (Potassium Lithium Aluminum Manganese Silicate Fluoride)
o Montdorite (Potassium Iron Manganese Magnesium Aluminum Silicate Fluoride)
o Norrishite (Potassium Lithium Manganese Silicate)
o Polylithionite (Potassium Lithium Aluminum Silicate Fluoride)
o Phlogopite (Potassium Magnesium Aluminum Silicate Hydroxide)
o Preiswerkite (Sodium Magnesium Aluminum Silicate Hydroxide)
o Siderophyllite (Potassium Iron Aluminum Silicate Hydroxide)
o Tainiolite (Potassium Lithium Magnesium Silicate Fluoride)
o Tetra-ferri-annite (Potassium Iron Silicate Hydroxide)
o Tetra-ferriphlogopite (Potassium Magnesium Iron Silicate Hydroxide)
NikhilV.Sherekar8390377801(M.Sc.GeologyGATE+SET+NET-CSIR-UGC-JRF-AIR28)

4. o Trilithionite (Potassium Lithium Aluminum Silicate Fluoride)
o Zinnwaldite (Potassium Lithium Iron Aluminum Silicate Hydroxide Fluoride)
The Brittle Micas:
Dioctahedral:
o Chernykhite (Barium Vanadium Aluminum Silicate Hydroxide)
o Margarite (Calcium Aluminum Silicate Hydroxide)
Trioctahedral:
o Anadite (Barium Potassium Iron Magnesium Aluminum Silicate Hydroxide)
o Bityite (Calcium Lithium Aluminum Beryllium Silicate Hydroxide)
o Clintonite (Calcium Magnesium Aluminum Silicate Hydroxide)
o Kinoshitalite (Barium Magnesium Aluminum Silicate Hydroxide)
The Interlayer-deficient Micas:
Dioctahedral:
o Brammallite (Sodium Aluminum Silicate Hydroxide)
o Glauconite (Potassium Sodium Iron Aluminum Magnesium Silicate Hydroxide)
o illite (Potassium Aluminum Silicate Hydroxide)
Trioctahedral:
o Wonesite (Sodium Magnesium Aluminum Silicate Hydroxide)
❖ Reserve
As per UNFC, the total resources of mica in the country as on 1.4.2010 are estimated at 5,32,237 tonnes out of which
1,90,741 tonnes are placed under reserves category and 3,41,496 tonnes under remaining resources category. Andhra
Pradesh leads with 41% share in country's total resources followed by Rajasthan (21%), Odisha (20%), Maharashtra
(15%), Bihar (2%) and the remaining 1% is in Jharkhand and Telangana together.
❖ Uses
The splitting property of mica combined with its flexibility, elasticity, resilience, toughness, low heat conductivity and
high dielectric smgth make the micas excellent electrical insulators. mica are included fabricated/manufactured mica,
including cut condensor films, discs and washers, bridges and spacers, cut mica plates, elecfrical heating elements, mica
capacitors, Mica powders – It is used to give the frost effect on Christmas card, and also on Christmas tree (Snow),
mica paper, Micanite - (mica sheets formed by the splitting are called micanite), mica paper products, glass bonded mica,
mica bricks, mica tapes etc.High quality mica is used in the manufacture of gauges, compass card, quarter wave plate and
in Geiger counter.Mica is also used in indtrial and domestic heating field, e.g. mica window in heating stove. It can also
be added to grease to increase its durability and giving it a better surface. It is a superior insulator. So in the electrical
industry it is used as thermal insulation, and in electronic equipment as electrical insulators.
It is used in paints as a pigment extender and also helps to brighten the tone of colored pigments. Its shiny and glittery
appearance makes it ultimate for toothpaste and cosmetics
Natural sheet mica is used in Electrical and Electronic industries in the form of blocks, splittings and films or built-up
mica called “micanite". Sheet mica is used in manufacturing fabricated and micanite products, such as, capacitors and
commutator segments. Micanite or built-up mica is partly overlapped, irregular shaped and arranged as splittings
cemented together with either an organic or inorganic binder. Other uses of sheet mica include gauge glasses of high
pressure steam boilers, diaphragms of oxygen-breathing equipment, marker dials of navigation compasses, quarter wave
plates for optical instruments, window covers for radiation pyrometers & thermal regulators, stove window, chimneys
for gas & petromax lamps, diaphragms in microwave transmitters and insulation wrappers for high tension radar coils.
Besides, high quality natural mica sheets are used in helium-neon lasers where mica sheet works as retardation plate of
late, mica washers are extensively used in Computer Industry.
In the Construction Sector, mica scrap/ground mica is used in jointing cement for gypsum boards, asphaltic
roofing’s and damp-proof seal, and insulation boards. Ground mica acts as reinforcing filler in plaster for textured
coatings. Mica is used in insulation bricks, slabs and tiles because of its excellent thermal and insulating properties. Dry-
ground 50 mesh mica is used in the flux coating for arc welding electrodes, with flux containing 3 to 5% mica powder.
In paints, mica in the form of powder is used as filler and as an extender because it provides a smoother consistency,
improved workability and imparts increased resistance to water penetration and weathering. It also facilitates suspension
due to its relatively low specific gravity and platy morphology. Mica is used mainly in four types of paints, such as,
bituminous emulsions, exterior paints, fire-retardant paints and pearlescent pigments. Mica is added to drilling fluids to
get off the lost circulation zones.
NikhilV.Sherekar8390377801(M.Sc.GeologyGATE+SET+NET-CSIR-UGC-JRF-AIR28)