Images
Formula: ☐Ca2(Mg5.0-4.5Fe2+0.0-0.5)
Si8O22(OH)2
Inosilicate (chain silicate), amphibole, forms a series with
actinolite
Crystal System: Monoclinic
Specific gravity: 2.99 to 3.03 measured, 2.964 calculated
Hardness: 5 to 6
Streak: White
Colour: Green, white, brown
Solubility: Insoluble in hydrochloric, sulphuric and nitric acid
Common impurities: Ti,Mn,Al,Na,K,F,Cl,H2O
Environments:
Metamorphic environments (common)
Tremolite is an amphibole. It is an important rock-forming mineral and
occurs most commonly as a component of metamorphosed carbonate rocks, especially
skarn and dolomite
marble, where the crystals and
aggregates can be quite large. In this environment it commonly forms as
pseudomorphs of tremolite after
diopside, but it can also be
primary. Tremolite is
common in many metamorphosed mafic and
ultramafic rocks such as
amphibolite,
although actinolite
and other iron-rich amphiboles usually dominate there.
Tremolite also may be found in
skarn
It is a mineral of the
albite-epidote-hornfels,
hornblende-hornfels,
greenschist,
amphibolite and
granulite facies.
Localities
The Two Mile and Three Mile deposits, Paddy's River, Paddys River District, Australian Capital Territory, Australia,
are skarn deposits at the contact between
granodiorite and volcanic rocks.
Tremolite is a primary silicate that occurs intergrown
with magnetite
(AJM 22.1.36).
At lots 10 and 11 of concession 1, Bathurst Township, Lanark County, Ontario, Canada (DeWitts corner), the deposit is
located in the Grenville Geological Province, which consists mostly of
marble, gneiss, and
quartzite.
Syenite-migmatite was
also reported in the area where the vein-dikes are located. Characteristic features of the vein-dikes include the
fact that perfectly formed euhedral crystals of different minerals can often be found floating in
calcite with no points of contact with the walls. Sometimes these crystals
have inclusions of calcite, irregular or rounded in shape. It has been argued
that at least some of the vein-dikes were formed as a result of melting of Grenville
marble.
Tremolite is rare and forms pale yellow and pale green crystals to 6 mm in yellow
calcite in lot 11
(R&M 97.6.556-564).
The Ma On Shan Mine, Ma On Shan, Sha Tin District, New Territories, Hong Kong, China, is an abandoned
iron mine, with
both underground and open cast workings. The iron ores contain
magnetite as the ore mineral and occur predominantly as masses of all sizes
enclosed in a large skarn body formed by contact metasomatism of
dolomitic limestone at the
margins of a granite intrusion. In parts of the underground workings
magnetite is also found in
marble in contact with the
granite. The skarn rocks
consist mainly of tremolite,
actinolite, diopside and
garnet.
Galena has been reported to occur in quartz veins cutting the
skarn
Tremolite is found abundantly in the skarn rocks, in intimate
association with actinolite; other associated minerals include
magnetite, garnet,
chlorite, mica and
fluorite
(Hong Kong Minerals (1991). Peng, C J. Hong Kong Urban Council)
Amity, Town of Warwick, Orange county, New York, USA, is an area of
granite intrusions into
marble and associated
gneiss. The marble is
mostly composed of white crystalline calcite that often has small flakes
or spheres of graphite and
phlogopite. Tremolite was found sporadically as elongated
brownish-green prisms embedded in white marble associated with
graphite. The tremolite is fluorescent bright blue
(R&M 96.5.440-441).
Tremolite from Amity - Image
At the Balmat-Edwards Zinc Mining District, St. Lawrence county, New York, USA, the
zinc and talc mines are well known for
hexagonite (a manganese-bearing variety of tremolite), as well defined
crystals embedded in schistose matrix. Emerald-green
chromium tremolite is also found occasionally, and also mountain
leather (a leather-like variety of tremolite). Some of the material may be admixed with
sepiolite
(R&M 97.2.142-151).
Tremolite from Balmat-Edwards - Image
The Calvin Mitchell farm, De Kalb, De Kalb Township, St. Lawrence county, New York, USA, has been mined for gem
diopside. Tremolite found here is colourless to grey, and often forms
epitactic overgrowths on diopside with alteration to
talc, creating pseudomorphs after
diopside. Crystals exceeding 15 cm are known, but they are almost always poorly
terminated
(R&M 97.2.144).
Tremolite from De Kalb - Image
At the Hall farm, Gouverneur, St. Lawrence county, New York, USA, exceptionally fine crystals of colourless to
dark green tremolite, up to 25 cm long, have been found in veins of
calcite. Good quality tourmaline and
calcite crystals have also been found here
(R&M 97.2.144-145).
Reese farm, Gouverneur, St. Lawrence county, New York, USA, is best known for its world class
fluor-uvite crystals, but it also hosts very fine colourless to white
tremolite crystals up to 10 cm. They are the most common lining found in veins, associated with
fluor-uvite and fluorapatite
(R&M 97.2.143).
Tremolite from Gouverneur - Image
The Washburn farm chrome tremolite occurrence, Macomb, Macomb Township, St. Lawrence county, New York, USA, is special in
that it is chromium-rich, and this element has led to tremolite crystals
of an unusually bright green colour. The crystals are translucent, striated and seldom well terminated
(R&M 97.2.149).
Tremolite from Washburn Farm - Image
At Power's Farm, Pierrepont, St. Lawrence Co., New York, USA, prismatic, dark green, striated tremolite crystals
up to 5 cm long have been found, sometimes doubly terminated. Tremolite is most commonly found as
pseudomorphs after diopside to
9 cm in length; rarely it is found as acicular transparent crystals to 1 cm
(R&M 97.2.148).
Tremolite from Pierrepont - Image
At the OBrien farm, North Russell, St. Lawrence county, New York, USA, green tremolite crystals up to 15 cm long
occur in veins, lining pockets and as loose material. Pargasite and
fluoro-pargasite also occur here
(R&M 97.2.146-147).
Jenne farm, Russell, St. Lawrence county, New York, USA, is known for huge tremolite crystals, over 50 cm long,
but they are seldom terminated
(R&M 97.2.145-146).
The Old Van Buskirk farm, Russell, St. Lawrence county, New York, USA, recently (2013) produced fine tremolite
crystals with excellent form and lustre, of a dark green to almost black colour. Some crystals have a thin coating of
talc
(R&M 97.2.147).
Tremolite from the Old Van Buskirk Farm - Image
At the Selleck Road locality, West Pierrepont, St. Lawrence county, New York, USA, tremolite occurs in
calc-silicate rock as well terminated, colourless to almost
black crystals, with medium green being dominant. Most are prismatic, but equant crystals are also found. Brownish-grey
quartz is a common associate
(R&M 97.2.148-149).
Tremolite from Selleck Road - Image
Alteration
During the progressive metamorphism of silica-rich dolostones the following approximate sequence of mineral
formation is often found, beginning with the lowest temperature product:
talc,
tremolite,
diopside,
forsterite,
wollastonite,
periclase,
monticellite
diopside, CO2 and H2O to tremolite,
calcite and quartz
5CaMgSi2O6 + 3CO2 + H2O =
Ca2Mg5Si8O22(OH)2 + 3CaCO3 + 2SiO2
Diopside is produced by the metamorphism of siliceous
dolostone, and if water is introduced at a later stage
tremolite may be produced from the above reaction, or by the reaction of diopside with
dolomite
(DHZ 2A p276)
diopside and antigorite to
forsterite, Mg-rich tremolite and H2O
2CaMgSi2O6 + 5Mg3Si2O5(OH)4 ⇌
6Mg2SIO4 + Ca2Mg5Si8O22(OH)2 + 9H2O
At 10 kbar pressure the equilibrium temperature is about 580oC
(amphibolite facies)
(SERC)
diopside, dolomite, CO2 and
H2O to tremolite and calcite
4CaMgSi2O6 + CaMg(CO3)2 + CO2 + H2O =
Ca2Mg5Si8O22(OH)2 + 3CaCO3
Diopside is produced by the metamorphism of siliceous
dolostone, and if water is introduced at a later stage
tremolite may be produced from the above reaction, or by the reaction of diopside
with CO2 and
H2O
(DHZ 2A p276)
dolomite, quartz and H2O to
tremolite, calcite and CO2
5CaMg(CO3)2 + 8SiO2 + H2O →
Ca2Mg5Si8O22(OH)2 + 3CaCO3 + 7CO2
This is a metamorphic reaction in dolomitic
limestone
(MOM p496)
dolomite and tremolite to
forsterite, calcite, CO2
and H2O
Ca2Mg5Si8O22(OH)2 + 11CaMg(CO3)2
→ 8Mg2SiO4 + 13CaCO3 + 9CO2 + H2O
(DHZ 5B p213)
dolomite, tremolite and forsterite to
diopside, enstatite
and H2O
Ca2Mg5Si8O22(OH)2 + Mg2SiO4 ⇌
2CaMgSi2O6 + H2O
At a pressure of 4 kbar the equilibrium temperature is about 840oC
(granulite facies)
(JVW p97)
serpentine and diopside
to tremolite, forsterite and
H2O
5Mg3Si2O5(OH)4 + 2CaMgSi2O6 ⇌
Ca2Mg5Si8O22(OH)2 + 6Mg2SiO4 +
9H2O + H2O
In lower grade assemblages associated with contact and regional metamorphism serpentine may form tremolite
and forsterite according to the above reaction
(DHZ 2A p271)
spinel and
tremolite to forsterite and
magnesio-hornblende
MgAl2O4 + Ca2Mg5Si8O22(OH)2 ⇌
Mg2SiO4 +
Ca2(Mg4Al)(Si7Al)O22(OH)2
This reaction occurs in some strongly metamorphosed serpentinite
(DHZ 1A p261)
talc and calcite to tremolite,
dolomite, CO2 and H2O
2Mg3Si4O10(OH)2 + 3CaCO3 +4SiO2 →
Ca2Mg5Si8O22(OH)2 +
CaMg(CO3)2 + CO2 +H2O
This is a low-grade metamorphic change, occurring at temperature between about 250oC and 450oC
(MOM)
talc, calcite and
quartz to tremolite, CO2 and H2O
5Mg3Si4O10(OH)2 + 6CaCO3 +4SiO2 →
3Ca2Mg5Si8O22(OH)2 + 6CO2 +2H2O
Metamorphism of siliceous carbonate rock causes the formation of hydrous phases such as talc
and tremolite
(DHZ 5B p127)
talc, calcite and
quartz to tremolite, CO2 and H2O
5Mg3Si4O10(OH)2 + 6CaCO3 +4SiO2 →
3Ca2Mg5Si8O22(OH)2 + 6CO2 +2H2O
(DHZ 5B p127, p213)
tremolite to diopside,
enstatite, quartz and H2O
Ca2Mg5Si8O22(OH)2 ⇌ 2CaMgSi2O6
+ 3MgSiO3 + SiO2 + H2O
At temperatures of 575oC and above tremolite is unstable and
alters to diopside and enstatite.
The equilibrium temperature for this reaction at 8 kbar pressure is 930oC
(granulite facies), with the equilibrium to
the right at higher temperatures, and to the left at lower temperatures (for the same pressure)
(KB p421, diagram p420, SERC)
tremolite and CO2 to dolomite,
talc and SiO2
☐Ca2Mg5Si2O22(OH)2 + CO2
⇌ 2CaMg(CO3)2 + Mg3Si4O10(OH)2
+ 4SiO2
In the greenschist facies
tremolite may be converted to
talc according to the above reaction
(DHZ 3 p127)
tremolite, anorthite and
clinochlore to tschermakite and H2O
3☐Ca2MgSi8O22(OH)2 + 8Ca(Al2Si2O8) +
2Mg5Al(AlSi3O10)(OH)8 ⇌
5☐Ca2(Mg3Al2)(Si6Al2)O22(OH)2 + 4H2O
(AM 76.998)
tremolite and calcite to diopside,
dolomite, CO2 and
H2O
Ca2Mg5Si8O22(OH)2 + 3CaCO3 ⇌
4CaMgSi2O6 + CaMg(CO3)2 + CO2 + H2O
The forward reaction is a diopside-forming metamorphic reaction
(DHZ 2A p249)
tremolite, calcite and quartz to
diopside, CO2 and H2O
Ca2Mg5Si8O22(OH)2 + 3CaCO3 + 2SiO2 →
5CaMgSi2O6 + 3CO2 + H2O
This is a medium-grade metamorphic change occurring at temperature between about 450oC and 600oC
(DHZ 2A p270, MOM)
tremolite and dolomite to
forsterite, calcite, CO2
and H2O
Ca2Mg5Si8O22(OH)2 + 11CaMg(CO3)2 →
8Mg2SiO4 + 13CaCO3 + 9CO2 + H2O
(DHZ 1A p264)
tremolite, dolomite and
H2O ⇆
hydroxylclinohumite, calcite
and CO2
Ca2Mg5Si8O22(OH)2 + 13CaMg(CO3)2
+ H2O ⇌ 2Mg9(SiO4)4(OH)2 + 15CaCO3 + 11CO2
(DHZ 1A p264).
tremolite and forsterite to
diopside, enstatite and H2O
Ca2Mg5Si8O22(OH)2 + Mg2SiO4 ⇌
2CaMgSi2O6 + H2O
At 4 kbar pressure the equilibrium temperature is 840oC
(granulite facies)
(JVW p97)
tremolite, tschermakite and
albite to pargasite and
quartz
☐Ca2Mg
(AM 92.4.491)
tremolite, zoisite,
corundum and H2O to tschermakite
3☐Ca2MgSi8O22(OH)2 +
2Ca2Al3[Si2O7][SiO4]O(OH) + 7Al2O3 + H2O ⇌
5☐Ca2(Mg3Al2)(Si6Al2)O22(OH)2
(AM 76.990)
Back to Minerals