Mica


Mica is a group of phyllosilicate minerals. The word mica is derived from the Latin word micare, meaning to glitter.If the group of minerals has perfect basal cleavage and capable of splitting into thin laminae then it is called mica. Mineralogists call micas sheet phyllosilicates because their molecules combine to form distinct layers. These layers can be seen in muscovite mica specimens because it can be split into very thin, flexible, transparent layers. This physical property is so distinctive that all minerals that cleave in this fashion are said to have micaceous cleavage. They crystallize in monoclinic system. Some varieties may contain iron, magnesium, lithium and fluorine, barium, manganese and vandium.

The 3 important types of mica minerals are
a) Muscovite
b) Biotite
c) Lepidolite

Muscovite is also known as potassium mica which is represented by the chemical formula H2KAl3(SiO4)3, biotite is also known as magnesium iron mica represented as (H2K)(Mg, Fe)3Al(SiO4)3 and lepidolite is known as lithium mica which is represented as K Li Al(OH, F)2Al(SiO4)3. And there are few less important mica minerals which are Paragonite or sodium mica, Phlogopite or magnesium mica, Zinnwaldite or lithium iron mica, Lepidomelane or iron mica.


OCCURRENCE AND GEOLOGICAL DEPOSITS

Mica is widely distributed and occurs in igneous, metamorphic and sedimentary regimes.Mica is found in pegmatites intruding mica schists. It is found to occur in book form in the pegmatites.The mode of formation of mica which is found in the form of small flakes to big slabs cleavable into the fine laminae. Mica pegmatite consists of quartz core with felspar on the sides adjoining the country rock, mica-schists. In the quartz and felspar zones, which usually form the core, the formation of mica is sparsely found and also the flakes are not big in size. Mica pegmatites have been found to occur in various shapes and sizes mostly occuring as lenses. They may occur as parallel veins, pipes or in massive form.

A largest deposit of mica is found in Kodarma district in Jharkhand state in India. China is also one of the major producer of mica followed by USA, South Korea, Canada and England. Flake mica is produced in the U.S is in deposited in metamorphic form.


PROPERTIES

  • Its color is from Ruby to green and sometimes yellow.
  • Mica has excellent dielectric strength. Dielectric strength is the ability to withstand high voltage without puncturing.
  • Mica has excellent chemical, physical and thermal resistant properties.
  • Thin transparent sheets of mica called isinglass do not shatter even when exposed to extreme temperature gradients.
  • It has specific gravity of 2.5 to 2.6.
  • Hardness of mica is 6.

Applications/ Uses

  • Isinglass are used for peepholes in boilers and lanterns since it posses high heat resistance capacity.
  • The principal use of ground mica is in gypsum wallboard joint compound, where it acts as filler and extender, provides smoother consistency, improves workability, and prevents cracking.
  • It is also used as an insulator in concrete block, home attics, and can be poured into walls.
  • Mica found use in equipment that encounters very high temperatures like rockets, missiles and jet engine ignition system.
  • Ground mica also used in the well-drilling industry as an additive to drilling mud.
  • It is used as filler, extender and as reinforcing agent in plastic industries.
  • Mica sheets are used to provide structure for heating wire in heating elements and can withstand up to 900 °C.

Question and Answers

1.What are the types of mica mineral? A.The 3 important types of mica minerals are a.Muscovite b.Biotite c.Lepidolite

2.What is the chemical formula for muscovite?
A.Muscovite is represented by the chemical formula H2KAl3(SiO4)3.

3.In which countries the mica mineral deposits are found?
A.The major deposition of mica is found in India, China, USA, Canada, England and South korea.

4.Mention few properties of mineral mica
A.
Mica has excellent dielectric strength. Dielectric strength is the ability to withstand high voltage without puncturing.
Mica has excellent chemical, physical and thermal resistant properties.

5.Give some applications of mica?
A.Isinglass are used for peepholes in boilers and lanterns since it posses high heat resistance capacity.
It is also used as an insulator in concrete block, home attics, and can be poured into walls.


References:
www.wikipedia.com,
www.mineralzone.com,
Mineral Information Institute - MICA.mht

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