Tremolite

tremolite

tschermakite

enstatite

tremolite

Images

Formula: ☐Ca2(Mg5.0-4.5Fe2+0.0-0.5) Si8O22(OH)2
Inosilicate (chain silicate), amphibole, forms a series with actinolite
Specific gravity: 2.99 to 3.03
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).

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).

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 97.2.149).

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).

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).

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).

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).

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).

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).

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
☐Ca2Mg5Si8O22(OH)2 + ☐Ca2(Mg3Al2)(Si6Al2)O22(OH)2 + 2Na(AlSi3O8) ⇌ 2NaCa2(Mg4Al)(Si6Al2)O22(OH)2 + 8SiO2
(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)

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