Mica Industry 03

8/8/2019 Mica Industry 03

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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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Mica Industry 03