What makes micas so important to command such a unique position ? Because it had been gifted with exceptional values. It possesses some of the most outstanding combination of chemical, physical, electrical, thermal and mechanical properties which are not found in any other product.
          
Processing
          
The ordinary mica crystals as they come out of a mine is in form of rough books or lumps of irregular shape, size and thickness, associated with impurities and structural imperfections. They have to undergo a long operation of cutting, sorting and processing from crude to commercial quality. The waste resulting from the production of crude to commercially useful sheet mica forms about 90 per cent Some times even the total output of mica from a mine is sold as scrap mica and it can be used as Mica Scrap or can be used for Grinding Mica Powder.
       
No machine has yet been designed to process mica mechanically. The processing technique, therefore, involves only a pair of hands, eyes and a simple knife. The operations performed consists of cobbing or cleaning the crude crystals as extracted from the mine with its associated impurities; rifting or splitting the cobbed mica into usable sheets by sickle and then by sharp knife removing major flaws and structural imperfections, such as cracks, holes, reeves, crossgrains and other physical defects to obtain the maximum usable area with minimum wastage. The trimming of mica is a skilled hand-operation in which cracks and imperfections are removed at the edges of the sheets using a knife while saving the best area of usable sheet. The knife-dressed sheet mica of irregular polygonal shapes is finally graded into different standard sizes and commercial qualities before they are offered for marketing.
       
Classification
      
For commercial and industrial purpose natural mica are mainly divided into three catagories,viz :

1. Processed Mica  2. Fabricated Mica  3. Manufactured Mica.

Processed Mica is fundamentally a natural sheet mica of an irregular size and polygonal shapes that is relatively flat and free from physical defects and structural imperfections having a minimum usable area of 4.8 sq. cm. (0.75 sq. inch), suitable to be cut, punched or stamped into specific size and shape chiefly for use by the electronic and electrical industries.

Fabricated Mica is basically a natural sheet mica cut, stamped or punched to specified size, shape and thickness for industrial and uses, such as; discs, washers, cut-films or sheets, joints, backing plates, plates, spacers, mica formers for irons, toasters, rice-cookers, etc.

Manufactured Mica means mica-based products manufactured from natural mica, such as, micanite or built-up mica, mica paper, mica heating elements, mica capacitors, mica flakes and powder, mica bricks, etc.
        
Quality grading of mica
       
The quality classification of mica, is based visual tests, depends on individual opinion. Also products of different mines vary in physical characteristics to such an extent that the development of a single standard with reasonable limits of tolerance becomes an acutely dificult task. Added to these difficulties are the facts that quality clasification has to be carried out by a large number of individual workers, and that it is highly influenced by such circumstantial factors as lighting conditions, mood of the inspector, etc. Under these circumstances any standard for quality classification of mica, such as the one described in this standard can give at best an approximate idea of a particular quality and its relative position with respect to other qualities. As such, the quality of mica depends upon the and the seller who have to work out a basis on mutual understanding and peculier requirements of the industrial applications. The application of common sense to the task of procurement is therefore always helpful especially so in the matter of choosing a right supplier as only an experienced supplier knowing the individual buyer’s specific requirements, is able to deliver to the near correct material. In fact, it is an expert’s job to process and assort mica to suit to individual buyers requirements and maintain uniform and satisfactory supplies on a regular basis.
          
Technical data of mica
     
Physically Mica is transparent, optically flat, easily splittable into thin films along its cleavage, colourless in thin sheets, resillient and incompressible.
    
Chemically Mica is a complex hydrous silicate of aluminium containing potassium, magnesium, iron, sodium fluorine and/or lithium and also traces of several other elements, It is stable and completely inert to the action of water, acids (except hydro-fluoric and concentrated sulphuric), alkalies, conventional solvents, oils and is virtually unaffected by atmospheric action.
        
Electrically Mica has the unique combination of great dielectric strength, uniform dielectric constant and capacitance stability, low power loss (high Q factor), high electrical resistivity and low temperature co-efficient and capacitance. It is noted for its resistance to arc and corona discharge with no permanent injury, and has little or no effect when exposed to electronic radiation dosages upto 10¹⁸ nvt. Thus maintaining its a-c dielectronic material when exposed to the oxidising action of electrical discharges either on the surface or within internal gas spaces in built-up mica insulation.
       
Thermally Mica is fireproof, infusable, incombustible and non-flammable and can resist temperatures of 600° C to 900° C (1112° F to 1652° F) depending on the type of mica. It has low heat conductivity, excellent thermal stability and may be exposed to high temperatures without noticeable effect.
        
Mechanically Mica is relatibility soft and can be hand-cut, machined or die-punched. It is flexible, elastic and tough, having high tensile strength. It can withstand great mechanical pressure perpendicular to plane but the lamination have weak cleavage and can be easily split into very thin leaves.
    

Uses and applications of natural sheet mica based on dielectric, optical, mechanical, electrical and thermal properties or their combination :
 

Commercial Quality	Applications
V-1 Ruby Clear V-2 Ruby Clear & S.S. V-3 Ruby Fair Stained V-4 Ruby Good Stained V-5 Ruby Stained "A" V-6 Ruby AQ V-14 Green / Brown V-14 1st Quality	Uses Based on dielectric properties : High precision electronic capacitors (fixed & trimmer) for transmission of radio  waves e.g. for Radio, and Guided Missiles, etc. Microwave transmission attenuators. Microwave tube Windows. Windows for geiger counter tube for measuring soft radiations detecting radio activity. X-ray apparatus and similar devices requiring protection from heat. Space Rockets. Telestar transmission Jet engine ignition systems Target and mosaic micas used in telecasting industry in image orthocones and computer matrix. Radiation insulation. Uses based on optical properties : Diaphragms in guided missiles. Inconoscope screen in television reflectors. Quarter-wave plates for optical instruments. Synthetic optical crystals. Marker dials for navigation compasses. High pressure steam boiler gauge glasses. Goggles. Window covers for radiation pyrometers and thermal regulators. Uses based on Mechanical properties : Diaphragms for oxygen breathing equipments. Diaphragms for detecting sound in submarine and air crafts. Resistance & Potentiometer cards.
V-5 Ruby Stained "A" V-7 Ruby Stained "B" V-8 Ruby BQ V-9 Ruby Heavy Stained V-15 Green / Brown V-15 2nd Quality V-16 Green / Brown V-16 Std. Or BQ	Uses based on Electrical Properties : Bridges and supports for radio, television and electronic Tubes, television cathod ray tubes, hearing aid tubes,audion tubes, acron tubes, miniature tubes, incandescent lamps, etc. Low precision and receiver condencers. Backing plates for capacitors. Interlayer insulation in high temperature air-cooled transformer coils. Supports for heating filaments of high power electric lamps. Insulation for Magnetos in ignition systems of internal combustion engines of submarines, aeroplanes, automobiles, trucks, military tanks, etc. Wrappers, shields and washers for spark plugs. Transistor Mounting Washers. Strainer Cores & Skin Gates for sand castings. Punched mica parts for Computers, Televisions, Radios, Car-ignitions and other semi-conductors and electronic components. Uses based on optical-cum-mechanical properties : Chimneys for gas and petromax lamps. Diaphragms for producing, receiving and transmitting sound Waves in telephones, head phones, radio-phones, phonographs, gramophones, sound boxes, loud speakers and telephone transmitter buttons. Window covers for combustion furnaces, anthracite lamps and oil stoves. Incandescent lamp Fuse plugs and sockets. Wrappers for insulating the high tension coil of radars. Heavy electrical equipments. Pyrometres. Stove mica for furnace peep holes and isinglass.
V-9 Ruby Heavy Stained V-10 Ruby Densely Stained V-11 Black Dotted V-12 Black Spotted V-13 Black/Red Stained	Uses based on the thermal properties : Various domestic electric heating applicances requiring non-inflammability and dielectric resistivity,viz. Cooking ranges, electric flat-irons, toasters, coffee perculators, kettles, ovens, rectifiers, soldering, irons, griddles, water heaters, radiaters, boilers, hair dryers, lead melting vats,glue pots, and host of other household appliances. Commutator segment insulation and armature insulation in motors and generators that are fully enclosed to exclude dust and moisture and those that are to be used in a very hot climate at high operating temperature. Solenoid insulation in electric motors and generators. Insulating washers, discs and terminal plates for dynamos, commutators, transformers, electric motors, generators, lightning arresters, fuse boxes, induction coils, grid rheostats and numerous other electrical devices.