Of the nine common varieties in the Mica group of minerals, the three principal classes of Mica of commercial importance are:
- Muscovite Mica: K Al2 (Al Si3 O10) (OH)2
- Phlogopite Mica: K Mg3 (Al Si3 O10) (OH)2
- Biotite Mica: K (Mg, Fe)3 (Al Si3 O10) (OH)2
Muscovite Mica
Muscovite Mica is a hydrous potassium aluminium silicate with a predominance of potassium. Having vitreous lustre, it ranges from colourless through brown to green or red. Muscovite Mica is transparent and harder than Phlogopite Mica; it has more widespread availability. It surpasses all Mica due to its superior properties and is, thus, identified as a necessary input for electrical and electronic applications as well as other industries. Vast exploitable reserves are found chiefly in India, which produces and markets over 80% of the total global output of Muscovite Mica. Indian Muscovite Mica is considered the finest in the world. Deposits are also located in Brazil, Chine, South Africa, and USA. Click here to open Muscovite Mica Analysis. Muscovite Mica can be divided into two colour groups:
Ruby Muscovite: Its colour ranges from almost white through pink to light ruby and into shades of brownish ruby and brown. It is produced in the Indian states of Jharkhand (formerly Bihar) and Rajasthan.
Green Muscovite: Its colour ranges from light to pale green through yellowish and olive green to dark green. It is produced in the Indian state of Andhra Pradesh.
Colour, per se, has minor influence on quality. Both Ruby Mica and Green Mica are equally suitable under normal working conditions. Still, Ruby Mica is generally preferred since at elevated temperatures, Green Mica displays erratic electrical characteristics. The structure of Green Muscovite is stable but less perfect as compared to Ruby Muscovite. Moreover, Ruby Muscovite is harder than Green Muscovite. It has excellent cleavage permitting it to be split into the thinnest desired film without the risk of cracking.
Phlogopite Mica
Phlogopite Mica is a hydrous magnesium aluminium silicate with a predominance of magnesium. It is commonly referred to as Amber Mica and varies in colour from amber or dark brown to light silver. Transparency is less than Muscovite Mica and its films are a bit cloudy. Phlogopite Mica is softer than Muscovite Mica, but has greater heat resistance and thermal durability. It is preferred where a combination of high heat stability at high temperature is required. Deposits are chiefly found and mined in Canada, Madagascar, Russia, and Sri Lanka. Click here to open Phlogopite Mica Analysis.
Biotite Mica
Biotite Mica is a phyllosilicate mineral with a predominance of iron, which gives it a dark hue. Having vitreous lustre, it ranges from black through dark brown to dark green. It is commonly referred to as Black Mica as against Muscovite or White Mica and Iron Mica because it is more iron-rich than Phlogopite Mica. Biotite Mica is opaque to translucent and softer than Muscovite Mica, but has incredible electrical and thermal insulation properties. It finds application in construction, decorative, electronic, paint, rubber and manifold industries. Vast exploitable reserves are found chiefly in India. Click here to open Biotite Mica Analysis.