2. About MICA { Introduction } Mica is produced in huge
proportion in India. In fact, India is one of the leading suppliers
of mica to the world. India alone accounts for a major portion of
the worlds export of block mica and mica splitting. Mica can
withstand high temperature as it is a bad conductor of electricity.
Moreover , it can also be split up into thin films. These
unrivalled properties of mica have actually made it indispensable
for the production of several electrical equipment. India produces
approximate 90% of the worlds mica. It is an indispensable
component of the electrical industry. India accounts for 60% of
mica embarking in international trade.
3. Etymology and History of Mica Mica gets its name from the
Latin word Mica which literally means a crumb and is assumed to be
the influenced by the world Micare, meaning To shine or glitter.
Mica is knows as Abharak or Abharak in Hindi. Mica has to be used
in India since ancient times. Finely powdered Mica have been
utilised for various applications, like for decoration. During the
Indian festival of Holi, coloured Gulal or Abeer used by Hindus in
various parts of the country consists of fine minute crystals of
mica. The majestic Padmanabhapuram Palace, 65 km from Trivandrum in
India, has coloured mica windows.
4. Rock with mica and Mica Ore Rock Mica Mica Ore
5. Mica Sheet and Mica Powder Mica Sheet Mica Powder
6. Padmanabhapuram Palace The majestic Padmanabhapuram Palace,
65 km from Trivandrum in India, has coloured mica windows.
7. Mode of occurrence Mica-minerals occur in igneous,
sedinientary and metamorphic rocks formed under different
geological conditions. While muscovite occurs in pegmatites of
acidic nature, phologopite mica is restricted to basic-pegmatite.
Lepidolite occurs in pegmatites associated with topaz. Commercial
biotite is found to occur mostly in biotite-schists.
8. Types of Mica There are two types of Mica available in the
world :- (1) Dioctahedral (2) TrioctahedraI In Trioctahedral mica,
the most common types found are: Muscovite (H2KAl3(SiO4)3,
Zinnwaldite (Li2K2Fe2Al4Si7O24), Biotite (H2K)(Mg,Fe)3Al(SiO4)3,
Lepidolite (H,K)2(Fe, Al)4(SiO4)5, and Phologopite H2KMg3Al(SiO4)3.
Where as Clintonite is Brittle mica.
9. Availability of Mica in World and India World Resources
India is the leading producer of muscovite mica followed by Brazil.
Other producing countries are the USA, Tanzania, Rhodesia and
Argentina. The USA generally produces scrap mica. The leading
producers of phologopite mica are Malagasy Republic and Tanzania
whose average annual production are 1,000 tonnes and 300 tonnes
respectively. Small production of phologopite is reported from
Canada, Tanzania and India.
10. Brazil Mica is found in a number of districts parallel to
the Atlantic coast. It is found in a belt 480 km long, 192 km wide.
Most of the production comes from Minas Gerais State. Minor
occurrences are reported from Bahia, Goyaz, Sao Paulo, Matto
Grosso, Ceara, Parahyba and Estado de Rio.
11. USA Mica production in this country chiefly comes from
Spruce Pine, Franklin- Sylva and Shelby Hickory districts of North
Carolina. Production is mostly that of scrap mica. It is obtained
during the mining of felspar and quartz. For blocks, splittings and
condenser films, the USA depends solely upon India and Brazil.
12. USSR Though Russia was the first country which reported
production of mica, it depends considerably on the imports from
India. Ruby mica is mined at Telinskoye in the Chupa district of
Karelia Peninsula. Green mica is mined near Kyshtym, north-west of
Chelyabinsk in the Urals. Mica-pegmatite veins in crystalline
schists have been located in Mama, Vitim, Chaya and Chara river
areas in Siberia. Phlogopite is mined near Trkutsk, south-western
end of Lake Baikal.
13. Malagasy Phlogopite occurs north-west of Fort Dauphin in
numerous pegmatite veins and occasionally in pockets, irregularly
distributed in an oblique or normal manner in beds of pyroxenites
which are usually interstratified in the crystalline schists of the
Ampandrandava and Tranomaro groups of the Androyan system. The
pyroxenite beds usually range in thickness up to 50 metres and
exceptionally upto 150 metres. The mica veins are extremely
irregular but generally range upto 1-5 metres thick.
14. Indian Resources Mica is widely available and distributed
in sedimentary, metamorphic and igneous regimes. Large size mica
crystals, utilized for various purposes, are usually mined from
granitic pegmatites. In India, Mica is widely available in
Karnataka, Bihar, Kolkata, Rajasthan, Gudur and Andhra Pradesh.
Hazaribagh, Gaya, and Munger districtsof Bihar account for a huge
proportion of the total production. These districts lie on the
northern fringe of Chota Nagpur Plateau.
15. Indian Resources The remaining half is evenly divided
between Nellore district in Andhra Pradesh and Bhilwara district in
Rajasthan. Mica is also mined in small quantities in Udaipur,
Sikar, Tonk and Ajmer districts of Rajasthan. Moreover , a small
portion is also mined in small quantity in Nilgiri district.
Production has been worsening due to artificial replacement. In
India, mica belt is located along the northern fringe of the Bihar
Plateau as includes parts of Hazaribagh and Gaya districts. Mica
belt generally occurs in the veins of the metamorphic rocks.
16. The mica belt in this region runs in the east-west
direction. Giridih, Domchanch and Kodarma are the principle
collecting centers where it is processed. This particular mica belt
produces more than half of the total mica production of the
country.
17. Properties of Mica Muscovite and Phlogopite are the most
commercially significant micas that have several uses. Micas value
is based on several of its unique physical properties. The
crystalline structure of mica forms layers which can be split into
thin sheets. The sheets are usually chemically inert, elastic,
dielectric, flexible, hydrophilic , platy, lightweight, reflective,
resilient, refractive, and range in opacity from transparent to
opaque. Due to the unique combination of physical, chemical and
thermal properties, low power loss factor, dielectric constant and
dielectric strength, Mica is precious in the electric
industry.
18. Properties of Mica The properties make mica ideal for use
in condensers, the basic function of which is to store
electrostatic energy in the dielectric field like low power loss
factor and dielectric constant d momentarily perhaps one-Millionth
part of a second and then to re-deliver the minimum possible loss.
The quality of Mica for commercial use depends largely on the
amount of staining, air inclusions, the degree of flatness and the
colour. No other natural substance has been found to possess the
properties equal to those of mica. Muscovite mica can be split into
flexible and transparent films as thin as 0.00025 inch, which gives
added advantage in making built-up mica, tapes and films that can
be used in any shape and size and punched films that can be used in
any shape and size and punched instruments and appliances
19. Silver Mica Capacitors
20. Uses and Applications of Mica Sheet mica is utilised in
numerous electrical and electronic appliances in different shapes
and sizes. Mica is used in equipments like condensers, sheostats,
transformers, electronic tubes and radar circuits as an insulating
material. Mica is also used in form of washers, discs, tubes and
plates. Nowadays mica is finding increasing use in equipment that
encounters very high temperatures like rockets, missiles and jet
engine ignition system. Phlogopite is used in spark plugs. Mica
films are used in alternate layers of binding materials like
shellac, alkyl or silicon resin and then pressed and baked.
21. In the electronic field, natural mica is mainly used in the
manufacture of capacitors such as bridge-spacers in electronic
valves and as panel-board where heat-resistance and low-loss
properties at high frequencies are required. The scrap mica
obtained during the processing of crude mica, is utilized in the
manufacture of mica bricks for heat insulation. Mica powder for use
as filler in rubber goods, plant, lubricant and to some extent in
plastic industries. It is also used in the manufacture of roofing
material, welding rod, wallpaper, lamp chimneys, shades etc Small
quantity of this mineral resource of the country is also used for
the production of mica powder and mica bricks.
22. Mica powder is used in the production of rubber goods and
paints. Mica bricks are used as an insulating material in steel and
thermal and petroleum refineries. Interestingly, the production of
mica depends on foreign demand to a great extent. Huge amount of
Mica in India is exported. Countries like United States, Japan and
United Kingdom are the major buyers of mica.
23. Methods of Grinding Scrap mica is ground by three
processes, namely:a) Dry Grinding b) Wet Grinding c) Micronising
The marketed product is classified according to the grinding
process which indicates quality and properties like colour, mesh
size and bulk density. Dry mica powder is prepared by grinding in
high speed hammer mills. The edges of the flakes get crushed and
powdered mica is produced which gives the appearance of flour.
Wet-ground mica is produced by grinding in water involving
preferential delamination of flakes. Churn mills, with large wheels
or rollers rotating on horizontal shafts are used for this
purpose.
24. References a.
http://www.mineralszone.com/minerals/mica.html b.
http://www.indianetzone.com/24/mica_indian_mineral resources.htm c.
http://en.wikipedia.org/wiki/Mica Submitted by :NAME:- BRAJ KISHOR
SAH ROLL NO.:- 112CR0126 2rd Year Student NIT Rourkela
