mica industry 03
TRANSCRIPT
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Presentation
OnMica Industry
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Contents
Introduction
History
Classification of Mica
1.Trioctahedral
2.Interlayer Deficient Micas
Occurrence
Manufacturing Process
Properties and Uses
1.Electronics2.Isinglass
3.Other
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Introduction
The word "mica" is thought to be derived from the Latin
word micare, meaning "to glitter", in reference to the
brilliant appearance of this mineral
The micagroup of sheet silicate (phyllosilicate) mineralsincludes several closely related materials having highly
perfect basal cleavage.
All are monoclinic with a tendency towards pseudo-
hexagonal crystals and are similar in chemical composition. The highly perfect cleavage, which is the most prominent
characteristic of mica, is explained by the hexagonal sheet-
like arrangement of its atoms.
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History
Human use of mica dates back to pre-historic times.
Mica was known to ancient Egyptian, Greek and Roman
civilizations, Chinese civilization, as well as the Aztec
civilization of the New World. Mica was also used in cave paintings in the Upper Paleolithic
period. The first hues were red (iron oxide, hematite, or red
ochre) and black (manganese dioxide, pyrolusite), though
black from juniper or pine carbons has also been discovered.
White from kaolin or mica was used occasionally.
The Pyramid of the Sun in Teotihuacan contains considerable
amount of mica in layers upto 30cm(12 in) thick.
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Classification of Mica
Chemically, micas can be given the general formula[1]
X2Y46Z8O20(OH,F)4
in which X is K, Na orCa ; Yis Al, MgorFe ; Zis
chieflySiorAl
Structurally, micas can be classed as dioctahedral (Y = 4)
and trioctahedral (Y = 6). If the X ion is K or Na the mica
is a common mica whereas if the X ion is Ca the mica is
classed as a brittle mica.
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Trioctahedral
These include ---
Common micas :
1.Phlogopite2.Biotite
3.Zinnwaldite
4.Lepidolite
5.Muscovite
Brittle micas :
1.Clintonite
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Scenario in India
The British Geological Survey reports that as of
2005, Koderma district in Jharkhand state in India
had the largest deposits of mica in the world.
Mica deposits are found in northern edge of the
Chota Nagpur plateau.
In Rajasthan the major mica producing are is around
A
jmer. Nellore mica belt ofA
ndhra Pradesh is also animportant producer of mica in the country.
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Manufacturing Process
Labourers go in field with chisel and hammer from vein to vein to
find out paying pegmatite veins.Mines are developed following the
veins.
The Room and Pillar method is adopted in Mining.The mica
obtained from the mine is called crude mica.It requires a littledressing to remove associated pegmatite dirt as well as defective
portions such as buckled, wrinkled and wavy mica.They are rifted
away with sickle.
Book-mica, split into a size atleast covering an area of 2 x 1 and
about 1/8 inch thick is called block mica. Block mica split into thinfilms of thickness 0.004-0.0012 inch is claled mica-film and less
than 0.0012 inch thick as splitting.
During processing a considerable amount of mica goes waste.This
waste mica is called Scrap mica.The ratio of scrap mica to crude
varies.
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Properties and uses
Electronics1. Mica has a high dielectric strength and excellent
chemical stability, making it a favoured material formanufacturing capacitors for radio frequencyapplications.
2. It has also been used as an insulator in high voltageelectrical equipment, and between the bars ofcommutators in direct current motors and generators.
3. Mica is used because it can be split into very thin slices,and this keeps its thermal resistance low while retainingsufficient dielectric strength to prevent current fromflowing across it at moderate voltages.
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Isinglass1. Thin transparent sheets of mica called "isinglass" were
used for peepholes in boilers and lanterns because they
were less likely to shatter compared to glass whenexposed to extreme temperature gradients.
2. Such peepholes were also used in "isinglass curtains" inhorse-drawn carriages and early 20th century cars.
ther1. Mica is also birefringent and is commonly used to make
quarter and half wave plates.
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2. Because mica can be pressed into a thin film, it is oftenused on Geiger-Mller tubes to detect low penetratingalpha particles.
3. Some brands of toothpaste include powdered white
mica. This acts as a mild abrasive to aid polishing of thetooth surface, and also adds a cosmetically-pleasing
glittery shimmer to the paste.
4. Mica is used in the production of pearlescent pigments.
5. Mica sheets are used to provide structure for heatingwire in heating elements and can withstand up to 900 C(1,650 F).Because mica is resistant to heat, it isused instead of glass in windows for stoves andkerosene heaters.
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Bibliography
http://www.mineralszone.com/minerals/mica.html
en.wikipedia.org/wiki/Mica
http://www.hindustanmineral.com/
www.britannica.com/EBchecked/topic/379747/mica
Deer, W. A., R. A. Howie and J. Zussman (1966)An Introduction to the Rock Forming Minerals,
Longman P. C. Rickwood (1981), The largest crystals
Google Images
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