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Actinolite Asbestos Under the Microscope

Actinolite Asbestos, Off Crossed Polars

Transmitted Off Crossed Polarized Light Illumination


Actinolite asbestos is a fibrous amphibole with the chemical composition Ca2(Mg,Fe) 5[Si8O22](OH) 2. It is one of the more hazardous asbestos minerals.

Significance in the Environment:

Actinolite had a rather limited commercial use and is encountered as an impurity in talc or vermiculite as often as it is as an intentionally added material. In materials with a significant talc content the amount of Actinolite can exceed 1%. It rarely exceeds 1% in vermiculite samples but handling vermiculite that contains Actinolite can result in respiratory exposures thousands of times higher than the allowable industrial exposure.

Characteristic Features:

Actinolite has refractive indices that overlap those of Anthophyllite but Actinolite in some orientations will show oblique extinction of from 7 to 21 degrees. Anthophyllite never shows oblique extinction. Actinolite has a high refractive index than Tremolite. Actinolite shows dispersion effects in high dispersion liquids of 1.620 or 1.630.

Associated Particles:

As an impurity it is generally found with high concentrations of talc or in bulk vermiculite. It was used as an additive in paint and ceramics, mastics, floor tiles, acoustic tiles, and other construction materials.


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