Blue asbestos

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Blue asbestos

<td">δ = 0.005 - 0.008<td">Strong<td">Pleochroism<td">X = blue, indigo; Y = yellowish green, yellow brown; Z = dark blue<td">References<td">[1][2][3][4]

Crystals of black riebeckite in alkaline pegmatite, near Évisa (Corsica, France).jpg
Black riebeckite in an alkaline pegmatite from Lindinosa near Évisa, Corsica, France
Category Silicate mineral
Chemical formula ☐Na2(Fe2+3Fe3+2)Si8O22(OH)2
Color Black, dark blue; dark blue to yellow-green in thin section
Crystal habit As prismatic crystals, commonly fibrous, asbestiform; earthy, massive
Crystal system Monoclinic - Prismatic
Twinning Simple or multiple twinning parallel to {100}
Cleavage Perfect on {110}, intersecting at 56° and 124°; partings on {100} and {010}
Fracture Conchoidal to uneven
Tenacity Brittle
Mohs Scale hardness 6
Luster Vitreous to silky
Refractive index nα = 1.680 - 1.698 nβ = 1.683 - 1.700 nγ = 1.685 - 1.706
Optical Properties Biaxial (-)
Streak Pale to bluish gray
Specific gravity 3.28 - 3.44
Diaphaneity Semitransparent

Blue asbestos, also called crocidolite asbestos, is one of the six types of asbestos. It is a variant of the mineral riebeckite. It is considered by many experts to be the most dangerous type of asbestos. It can cause cancer and asbestosis. It was formerly used in Kent brand cigarettes as a filter material. It is rare in construction compared to white asbestos, but it is sometimes found in caulking, cement, wallboard, rope, and numerous other products. Due to its hazards, blue asbestos is no longer mined commercially.

Sources[change | change source]

  1. "Riebeckite", Handbook of Mineralogy, Mineral Data Publishing, 2001
  2. "Riebeckite",
  3. "Riebeckite", The Mineralogy Database (
  4. IMA Master List

Other pages[change | change source]

Other websites[change | change source]