The D-line refractive index across the width of this sample of tremolite asbestos is about 1.603. It matches the
refractive index of the Cargille High Dispersion 1.605 liquid at a wavelength of about 660 nanometers. At this
wavelength the Cargille liquid has a refractive index of about 1.597, as does the tremolite. This Type of Dispersion
Staining produces a single color for any given wavelength match between a given liquid and solid with a fixed single
linear polarizing filter. Oblque condensor darkfield dispersion staining produces the same colors as objective cental
stop dispersion staining but the particles are in much better focus. As a result it is easier to see the particles that
are producing the effect.
Transmitted Oblique Darkfield Dispersion Staining, Single Polarizing Filter Perpendicular to Length
Tremolite asbestos is a fibrous amphibole with the chemical composition
Ca2Mg 5[Si8O22](OH) 2. It is one of the more hazardous asbestos
Significance in the Environment:
Tremolite 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 Tremolite can exceed 1%.
It rarely exceeds 1% in vermiculite samples but handling vermiculite that contains Tremolite can result in respiratory
exposures thousands of times higher than the allowable industrial exposure.
Tremolite has refractive indices that overlap those of Anthophyllite but Tremolite in some orientations will show oblique
extinction of from 7 to 21 degrees. Anthophyllite never shows oblique extinction. Tremolite has a lower refractive index
than Actinolite. Tremolite shows dispersion effects in high dispersion liquids of 1.605.
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. Because of its purity it
was often used as a filter material or crucible liner in chemical analyses.
1. Asbestos Textile Institute, HANDBOOK OF ASBESTOS TEXTILES, 3RD EDITION, 1967.
2. Campbell, W.J., R.L. Blake, L.L. Brown, E.E. Cather, and J.J. Sjoberg, IC 8751; SELECTED SILICATE MINERALS AND THEIR
ASBESTIFORM VARIETIES, US Dept. of the Interior, Bureau of Mines Information Circular, 1977
3. Deer, W. A., R. A. Howie, and J. Zussman, AN INTRODCUTION TO THE ROCK-FORMING MINERALS, ISBN 0-582-30094-0, pp. 22-6,
4. Ledoux, R. L. (ed), SHORT COURSE IN MINERALOGICAL TECHNIQUES OF ASBESTOS DETERMINATION, Mineralogical Association of
5. Levadie, Benjamin (ed), DEFINITIONS FOR ASBESTOS AND OTHER HEALTH-RELATED SILICATES, ASTM STP 834, 1984.
6. Riordon, P. H. (ed), GEOLOGY OF ASBESTOS DEPOSITS, Society of Mining Engineers, 1981.
7. World Health Organization, ASBESTOS AND OTHER NATURAL MINERAL FIBRES, Environmental Health Criteria 53, 1986.