The word Mica is derived from the Latin word “micare”, which means “to shine”, in reference to its glittering effect when exposed to light. Mica is a non-metallic mineral that exhibits perfect basal cleavage. The mica group represents a total of 37 different types of mica. Muscovite and Phlogopite are important micas for commercial application. Muscovite is by far the most frequently mined and used type of mica. A typical chemical composition of Muscovite Mica is silica (SiO2) – 45%; alumina (Al2O3) – 38%; potassium oxide (K2O) – 12%; other – 5%.

Varied properties – Multiple uses

Mica’s reflective optical properties are utilized in cosmetics as well as in paints & coatings. Besides it’s glittering and aesthetic effects, mica is used in a wide range of industrial applications. The construction and plastic industries use mica as a functional filler. Given its diverse properties and applications, mica is found in a significant number of parts and materials used in the automotive industry. Mica can withstand high temperature which makes it a useful component for welding and frictional systems. Mica is used as a lubricant in the oil & gas drilling sector.

Some important characteristics of Mica

  • Chemically inert, i.e. it does not react to water, acids, oil or solvents.
  • Lightweight, flexible and strong.
  • Resists extremely high temperatures and sudden changes in temperature.
  • Withstands high voltages and insulates with low power loss.
  • Absorbs and reflects light, which enables a decorative effect and protects against ultra-violet (UV) light.

Types of Mica

MICA TYPE Composition formula Characteristics
Muscovite KAl2(AlSi3)O10(OH)2 Rude ore is a brownish natural platy mineral. Octahedral ions in a crystal are mostly occupied with Al.
Phlogopite KMg3(AlSi3)O10(OH)2 Phologopite is darker than muscovite and soft. Octahedral ions in a crystal is mostly occupied with Mg.
Sericite KAl2(AlSi3)O10(OH)2 Rude ore is a greenish gray, natural platy mineral, same composition as muscovite but its smaller crystals due to hydrometamorphism
Synthetic Fluoro Phlogopite KMg3(AlSi3)O10F2 Synthetic fluorophlogopite, contains no (OH) of the natural phlogopite instead the (OH)- is fully substituted with F. White and a little rigid.

Properties of Muscovite Mica

Physical property Unit Value referring to literature etc.
True specific gravity kg/m3 (2.6~3.2)×103
Mohs hardness - 2.0~3.2
Specific heat J/kg・K 860~870
Thermal conductivity (in direction perpendicular to a cleavage surface) J/m・s・K 0.67
Dehydrating temperature of OH in crystal 550
Melting point 1,250
Ignition loss (900℃-3hr) wt% 4~5
Tensile strength Pa (25~30)×107
Dielectric breakdown voltage kV/0.1mm 18~25
Relative permittivity (50Hz) - 6.5~9
Dielectric loss tangent (50Hz, 25℃) % 0.01~0.02
Volume resistivity Ω・m 1010~1013
Coefficient of liner expansion m/m・K 3.6×10-5
Refractive index - nα=1.552~1.576