Mica

Mica HSN:25252020

Any of several silicates of varying chemical composition but with similar physical properties and crystalline structure. All characteristically cleave into thin sheets which are flexible and elastic. Synthetic mica is available. It has electrical and mechanical properties superior to those of natural mica; it is also water-free.

Properties: Soft, translucent solid; d 2.6-3.2. Mohs hardness 2.8-3.2, refer index 1.56-1.60, dielectric constant 6.5-8.7, noncombustible, heat-resistant to 600C, colorless to slight red (ruby), brown to greenish-yellow (amber).

Derivation: From muscovite (ruby mica), phlogopite (amber mica), and pegmatite. Synthetic single crystals are "grown" electrothermally.

Occurrence: US, Canada, India, Brazil, Malagasy Republic.

Forms: Block, sheet, powder, single crystals.

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Grade: Dry-ground, wet-ground.

Hazard (dust): Irritant by inhalation, may be dam- aging to lungs.

Use: Electrical equipment, vacuum tubes, incan- descent lamps, dusting agent, lubricant, windows in high-temperature equipment, filler in exterior paints, cosmetics, glass and ceramic flux, roofing, rubber, mold-release agent, specialty paper for insulation and filtration, wallpaper and wall- board joint cement, oil-well drilling muds.