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(repeating unit)
IMA symbolTr[1]
Strunz classification9.DE.10
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
(same H-M symbol)
Space groupC2/m (no. 12)
Unit cella = 9.84 Å, b = 18.02 Å
c = 5.27 Å; β = 104.95°; Z = 2
ColorWhite, gray, lavender to pink, light green, light yellow
Crystal habitElongated prismatic, or flattened crystals; also as fibrous, granular or columnar aggregates
TwinningSimple or multiple, common parallel to {100}; rarely parallel to {001}
CleavagePerfect on {110} at 56° and 124°; partings on {010} and {100}
Mohs scale hardness5–6
LusterVitreous and silky
DiaphaneityTransparent to translucent
Specific gravity2.99–3.03
Optical propertiesBiaxial (−)
Refractive indexnα = 1.599 – 1.612 nβ = 1.613 – 1.626 nγ = 1.625 – 1.637
Birefringenceδ = 0.026
2V angleMeasured: 86° to 88°
Ultraviolet fluorescenceShort UV=yellow, Long UV=range pink

Tremolite is a member of the amphibole group of silicate minerals with composition Ca2(Mg5.0-4.5Fe2+0.0-0.5)Si8O22(OH)2. Tremolite forms by metamorphism of sediments rich in dolomite and quartz, and occurs in two distinct forms, crystals and fibers. Tremolite forms a series with actinolite and ferro-actinolite. Pure magnesium tremolite is creamy white, but the color grades to dark green with increasing iron content. It has a hardness on Mohs scale of 5 to 6. Nephrite, one of the two minerals known as the gemstone jade, is a green crystalline variety of tremolite.

The fibrous form of tremolite is one of the six recognised types of asbestos. This material is toxic, and inhaling the fibers can lead to asbestosis, lung cancer and both pleural and peritoneal mesothelioma. Fibrous tremolite is sometimes found as a contaminant in vermiculite, chrysotile (itself a type of asbestos) and talc.


Tremolite from the Aure Valley, French Pyrenees (size: 8.2 × 6.7 cm)
Crystalline tremolite

Tremolite is an indicator of metamorphic grade since at high temperatures it converts to diopside.

Tremolite occurs as a result of contact metamorphism of calcium and magnesium rich siliceous sedimentary rocks and in greenschist facies metamorphic rocks derived from ultramafic or magnesium carbonate bearing rocks. Associated minerals include calcite, dolomite, grossular, wollastonite, talc, diopside, forsterite, cummingtonite, riebeckite and winchite.[3]

Tremolite was first described in 1789 for an occurrence in Campolungo, Piumogna Valley, Leventina, Ticino (Tessin), Switzerland.[2]

Fibrous tremolite


One of the six recognized types of asbestos, approximately 40,200 tons of tremolite asbestos is mined annually in India.[7] It is otherwise found as a contaminant.

See also

  • Libby, Montana – location of asbestos-related ailments caused by tremolite


  1. ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. ^ a b Mindat.org
  3. ^ a b Handbook of Mineralogy
  4. ^ Webmineral data
  5. ^ IMA Master List
  6. ^ Hawthorne, F. C.; Oberti, R.; Martin, R. F. (1 October 2006). "Short-Range Order in Amphiboles from the Bear Lake Diggings, Ontario". The Canadian Mineralogist. 44 (5): 1171–1179. Bibcode:2006CaMin..44.1171H. CiteSeerX doi:10.2113/gscanmin.44.5.1171.
  7. ^ Furquan, Ahmad Ansari. "Asbestos: Foe or Friend?". Indmedica Cyber Lectures. Indmedica. Retrieved 2 January 2012.