Chemical formula: Na2Mg1.5Fe2+1.5Fe3+2[Si8O22](OH)2 - Na2Fe2+3Fe3+2[Si8O22](OH)2
Sources: South Africa and Australia
Crocidolite is the name for asbestiform riebeckite. It is also known as “blue asbestos”. It is a fairly rare form of asbestos. It has excellent acid resistance and is a non-conductor of electricity. The fibers have greater tensile strength but lower heat resistance than chrysotile.
Crocidolite is a monoclinic solid solution amphibole so there is some variation in the chemical composition. Crocidolite chemistry is characterized by its Sodium content. There can be substitution between Magnesium and Iron.
By Polarized Light Microscopy (PLM) the prismatic crystals of crocidolite fibers tend to be thin and needle like. Crocidolite is monoclinic and has a negative sign of elongation. Its strong pleochroism aids in its identification. Its negative sign of elongation is also characteristic. The refractive indices range from approximately 1.670-1.717. It is a member of the amphibole double chain silicate group. Random orientation SAED of Crocidolite shows a layerline spacing of 5.3 Å with twinning sometimes present.
Negative sign of elongation
Fibers appear long and straight much like Amosite but much thinner, more like chrysotile
Acid storage battery casings
Spray on Insulation
Millboards (commercial ovens and steam pipes)
Transite paneling along with chrysotile and amosite