Tremolite

{{short description|Amphibole, double chain inosilicate mineral}}

{{Infobox mineral

| name = Tremolite

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| image = Tremolite Campolungo.jpg

| imagesize = 300px

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| category = Inosilicates

| formula = Ca₂(Mg_5.0-4.5Fe²⁺_0.0-0.5)Si₈O₂₂(OH)₂

| IMAsymbol = Tr{{Cite journal|last=Warr|first=L.N.|date=2021|title=IMA–CNMNC approved mineral symbols|journal=Mineralogical Magazine|volume=85|issue=3|pages=291–320|doi=10.1180/mgm.2021.43|bibcode=2021MinM...85..291W|s2cid=235729616|doi-access=free}}

| molweight =

| strunz = 9.DE.10

| dana =

| system = Monoclinic

| class = Prismatic (2/m)
(same H-M symbol)

| symmetry = C2/m (no. 12)

| unit cell = a = 9.84 Å, b = 18.02 Å
c = 5.27 Å; β = 104.95°; Z = 2

| color = White, gray, lavender to pink, light green, light yellow

| colour =

| habit = Elongated prismatic, or flattened crystals; also as fibrous, granular or columnar aggregates

| twinning = Simple or multiple, common parallel to {100}; rarely parallel to {001}

| cleavage = Perfect on {110} at 56° and 124°; partings on {010} and {100}

| fracture =

| tenacity = Brittle

| mohs = 5–6

| luster = Vitreous and silky

| streak = White

| diaphaneity = Transparent to translucent

| gravity = 2.99–3.03

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| polish =

| opticalprop = Biaxial (−)

| refractive = n_α = 1.599 – 1.612 n_β = 1.613 – 1.626 n_γ = 1.625 – 1.637

| birefringence = δ = 0.026

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| 2V = Measured: 86° to 88°

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| fluorescence = Short UV=yellow, Long UV=range pink

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| references = [http://www.mindat.org/min-4011.html Mindat.org][http://rruff.geo.arizona.edu/doclib/hom/tremolite.pdf Handbook of Mineralogy][http://webmineral.com/data/Tremolite.shtml Webmineral data][http://pubsites.uws.edu.au/ima-cnmnc/ IMA Master List]{{cite journal |last1=Hawthorne |first1=F. C. |last2=Oberti |first2=R. |last3=Martin |first3=R. F. |title=Short-Range Order in Amphiboles from the Bear Lake Diggings, Ontario |journal=The Canadian Mineralogist |date=1 October 2006 |volume=44 |issue=5 |pages=1171–1179 |doi=10.2113/gscanmin.44.5.1171|bibcode=2006CaMin..44.1171H |citeseerx=10.1.1.554.3335 }}

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Tremolite is a member of the amphibole group of silicate minerals with composition Ca₂(Mg_5.0-4.5Fe²⁺_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.