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Formula: CaCO3
Carbonate, trigonal paramorph of hexagonal
vaterite and orthorhombic aragonite
Specific gravity: 2.7102(2)
Hardness: 3
Streak: White
Colour: Colourless, white, yellow, red, orange, blue, green, pink, purple
Solubility: Readily soluble in hydrochloric, sulphuric and nitric acid
Common impurities: Mn,Fe,Zn,Co,Ba,Sr,Pb,Mg,Cu,Al,Ni,V,Cr,Mo
Environments:
Pegmatites
Carbonatites (essential)
Sedimentary environments (typical)
Metamorphic environments
Hydrothermal environments
Basaltic cavities
Calcite is a common and widespread mineral. It occurs in limestone,
marble and chalk, in all of which it is essentially
the only mineral present. It is an
important constituent of calcareous
marl and calcareous sandstone.
Water
carrying calcium carbonate in solution and evaporating in limestone caves often deposits
calcite as stalagtites, stalagmites and incrustations. Both hot and cold calcium-bearing spring water may form around the mouths of
the springs
cellular deposits of calcite in the form of limestone, known as travertine (formed by hot
mineral springs) or
tufa (formed when carbonate minerals precipitate out of ambient temperature water). Calcite occurs as a
primary mineral in some igneous rocks such as
nepheline syenite,
carbonatites and
pegmatites.
It is a late crystallisation product in cavities in lavas, and it is also a
common mineral in the oxidation zone of hypothermal (high temperature),
mesothermal (moderate temperature) and
epithermal (low temperature) hydrothermal veins associated with sulphide ores.
Carbonates such as calcite are essential constituents of
kimberlite.
Calcite is an essential constituent of
limestone,
marl and
skarn.
It is a common but not essential constituent of
sandstone.
It also may be found in
dolostone.
Calcite may occur in all metamorphic facies with the exception of the very high-grade
eclogite facies.
Selected 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.
Calcite is a primary carbonate that occurs as
interstitial material in magnetite ore and in veins. At the Three Mile
deposit it occurs in marble with
chlorite and talc. At the Two Mile
deposit red fluorescing calcite occurs as coatings on magnetite
(AJM 22.1.38).
At Bundoora, inner Melbourne, Victoria, Australia, ferroan calcite occurs in cavities in
basalt
as orange balls and bow-ties
(AJM 20.1.33-37).
At the Hohe Tauern mountains, Salzburg, Austria, magnesite
pseudomorphs after calcite have been found
(KL p156).
At Irai, Brazil, quartz pseudomorphs
after calcite have been found
(KL p247).
At Yellow lake, near Ollala, British Columbia, Canada, brewsterite casts
after calcite (pseudomorphs) have been found
(KL p268).
White to creamy off-white calcite is found as complex rounded crystals perched on
zeolites, especially brewsterite. Yellowish
calcite is abundantly found as infillings of zeolite-lined vesicles, larger vugs
and fracture seams
(R&M 96.6.520).
At the Faraday mine, Faraday Township, Hastings county, Ontario, Canada, spectacular specimens of slender scalenohedral
calcite occur, coated with hematite and botryoidal
goethite
(Canadian Museum of Nature specimen, R&M 94.5.410).
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.
Calcite is the most abundant constituent of the vein-dikes. It forms local aggregates of salmon-pink, yellow or
grey masses. The best-formed small spinel crystals, less than 10-mm in size,
have been found in the salmon-pink calcite, whereas the best larger spinel
crystals and the best pseudomorphs of
corundum after spinel appear to
occur in grey calcite toward the centre of
the vein-dikes
(R&M 97.6.556-564).
At the Thunder Bay Amethyst Mine, Thunder Bay District, Ontario, Canada, calcite has been found
with sulphide inclusions
(R&M 94.4.331-332).
At the Pioneer quarry, Kwun Tong District, Kowloon, Hong Kong, China, the contact between
granite and tuff is very sharp,
and many veins and stringers of aplite and
pegmatite from the batholith invade the country rock. The
granite near the contact contains crystals of
fluorite, pyrite,
molybdenite and quartz, and
calcite-filled vugs. Calcite also
occurs along joint planes
(Geological Society of Hong Kong Newsletter 1.7.6).
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.
Calcite occurs in veins or vugs in the skarn zone, associated with
fluorite, quartz,
pyrite or serpentine
(Hong Kong Minerals (1991). Peng, C J. Hong Kong Urban Council)
The Lin Fa Shan deposit, Tsuen Wan District, New Territories, Hong Kong, China, is located in a remote area of the Tai Mo Shan
Country Park, on a steep west facing slope of Lin Fa Shan, just above the abandoned village of Sheung Tong. The
surrounding hillsides are covered with shallow excavations, representing past searches for
wolframite, the natural ore of
tungsten. The abandoned workings are extremely dangerous with unsupported tunnels, open shafts and no maintenance since
their closures in 1957; the workings should not be entered
(http://industrialhistoryhk.org/lin-shan).
Lamellar calcite occurs in veins in the tungsten mine associated with
fluorite, quartz and
pyrite
(Hong Kong Minerals (1991). Peng, C J. Hong Kong Urban Council).
The Bairendaba Ag-polymetallic deposit, Hexigten Banner, Chifeng City, Inner Mongolia, China, is a mesothermal
magmatic-hydrothermal vein-type silver -
lead - zinc deposit, hosted in
Hercynian (about 419 to 299 million years ago) quartz
diorite.
It is suggested that, with decreasing temperature, mineral compositions changed progressively from
tungstate and oxide, to diatomic sulphide, to simple sulphide, to an
antimony sulphosalt mineral, and finally to an
antimonide.
Calcite has been found as flattened, white, rhombohedral crystals to over 2 cm, associated with and included
by dark gray acicular crystals of boulangerite
(Minrec 53.347-359).
At the Tantara mine, DR Congo, shattuckite
pseudomorphs after calcite have been found with
dioptase
(KL p230).
At Canaveille, Pyrenees, France, posnjakite and
langite pseudomorphs after
calcite have been found
(KL p193).
At Idar-Oberstein, Birkenfeld, Rhineland-Palatinate, Germany, quartz
pseudomorphs after calcite have been found
(R&M 95.3.275).
At Jalgaon, Maharashtra province, India, chalcedony
pseudomorphs after
calcite on chalcedony have been found
(KL p255).
At Agrigento, Sicily, Italy, calcite pseudomorphs after
aragonite have been found, with sulphur
(KL p151).
At Santa Eulalia, Mexico, calcite pseudomorphs after
baryte have been found
(KL p152).
At the Tsumeb mine, Namibia, mottramite
pseudomorphs after calcite have been found
(KL p202).
At the Olenitsa River, White Sea Coast, Karelia Republic, Russia, calcite
pseudomorphs
after ikaite have been found; these pseudomorphs are
called glendonites. Ikaite is formed at sub-zero temperatures and at room
temperature it rapidly dehydrates to calcite, and the glendonites so formed are
exceedingly fragile and collapse easily to a white powder
(R&M 97.6.496-509).
At Dalnegorsk, Primorsky Krai, Russia, calcite pseudomorphs after
fluorite have been found, with a quartz coating
(KL p153).
At Calvinia, near Capetown, Cape Province, South Africa, prehnite
pseudomorphs after calcite have been found
(KL p240).
At Asar hill, Güğtı, Dursunbey district, Balikesir province, Marmara region, Turkey,
quartz
pseudomorphs after calcite have
been found
(KL p248).
From Wheal Wrey, Wrey and Ludcott United Mines, St Ive, Cornwall, England, UK, specimen BM.1964,R5426 from the
Natural History Museum, London, features colourless, translucent, blocky prismatic crystals of
calcite, sprinkled with cubic microcrystals of pyrite
(RES2 p147).
At the Calton Hill quarry, Buxton, Derbyshire, England, UK, calcite crystals have been found coloured red by iron oxide, on
quartz associated with minor goethite
(RES p115, 116).
At the Odin mine, Castleton, Derbyshire, England, UK, calcite crystals have been found on dark purple
fluorite
(RES p129).
At Millclose mine, Darley Dale, Derbyshire, England, UK, calcite crystals have been found on a matrix of
sphalerite and fluorite, some with minor
pyrite and chalcopyrite
(RES p95).
At Eyam, Derbyshire, England, UK, calcite is associated with sphalerite,
fluorite and galena
(RES p117).
At Ladywash mine, Eyam, Derbyshire, England, UK, calcite crystals have been found with a dusting of minute
pyrite crystals, and calcite occurs on a fluorite -
limestone matrix
(RES p119, 120).
At the Riber mine, Matlock, Derbyshire, England, UK, calcite has been found with inclusions of
chalcopyrite, malachite and
copper, with occasional pyrite and rarely
bornite
(RES p68).
At the Magpie mine, Sheldon, Derbyshire, England, UK, calcite crystals have been found with a dusting of minute
pyrite crystals
(RES p115).
At the Hampstead Farm quarry, Chipping Sodbury, Gloucestershire, England, calcite crystals dusted with
pyrite have been found, also calcite on
pyrite
overgrowing baryte, and calcite on
marcasite
coating
baryte
(RES p172, 173).
At Croft quarry, Blaby, Leicestershire, England, UK, several generations of calcite have been identified. It has been found with minor
analcime on altered tonalite matrix.
Pseudomorphs of calcite after laumontite
have been found here, sometimes associated with later crystals of analcime
(RES p186-190, R&M 20.9-12).
At Enderby Warren Quarry, Enderby, Blaby, Leicestershire, England, UK, calcite occurs in
quartz-diorite and
tonalite associated with palygorskite
and dolomite
(R&M 20.13).
At Granitethorpe quarry, Sapcote, Blaby, Leicestershire, England, UK, joint-planes in the diorite
were sometimes coated with green-stained calcite or opal and some of the joints were slickensided
and contained a film of calcite
(JRS 20.13).
At Lane's Hill quarry, Stoney Stanton, Blaby, Leicestershire, England, UK, a specimen has been found which showed three generations of
Fe-bearing dolomite followed by calcite deposition
(JRS 20.13).
At the Church Gresley opencast coal mine, Ashby-de-la-Zouch, Northwest Leicestershire, Leicestershire, England, calcite
occurs in
septarian nodules
(RES p226, 227).
At Breedon quarry, Breedon on the Hill, Northwest Leicestershire, Leicestershire, England, UK, iron-stained calcite
crystals have been
found covered with small acicular crystals of malachite
(RES p203).
At Cloud Hill quarry, Breedon on the Hill, Northwest Leicestershire, Leicestershite, England, UK, calcite has been
found with inclusions of
chalcopyrite. Also a specimen has been found with minor attached
dolomite
(RES p205, 208).
At Lord Ferrises mine, Staunton Harold, Northwest Leicestershire, Leicestershire, calcite occurs with
galena, baryte,
sphalerite and chalcopyrite on
dolomitised limestone
(RES p218 to 223).
At Barrasford Quarry, Chollerton, Northumberland, England, UK, small amounts of calcite in have been found in vesicles associated with
both datolite and pectolite
(JRS 21.7-7).
At Wotherton mine, Chirbury, Shropshire, England, UK, calcite occurs with chalcopyrite,
pyrite and baryte
(RES p285, 286).
At Snailbeach mine, near Minsterley, Shropshire, England, UK, calcite occurs with
sphalerite
and also with harmotome, quartz,
chalcopyrite or galena
(RES p270 to 275).
At Llynclys quarry, near Oswestry, Shropshire, England, UK, calcite occurs with
dolomite
(RES p294).
At Tankerville mine, Worthen, Shropshire, England, UK, calcite occurs with galena
(RES p281).
At Cauldron Low quarry, Staffordshire, England, UK, calcite occurs with galena and
sphalerite on limestone
(RES p313).
At the Ecton mine, Staffordshire, England, UK, calcite occurs with
chalcopyrite
(RES p305 to 307).
At Hartshill, Nuneaton, Warwickshire, England, UK, manganoan calcite has been found with
manganite
(RES p321).
At Judkins quarry, Nuneaton, Warwickshire, England, UK, calcite has been found with baryte
(RES p323).
At Glen Brittle, Minginish, Isle of Skye, Eilean á Chèo, Highland, Scotland, UK, vesicles are abundant in
basaltic lava, mostly filled with
mordenite-quartz intergrowths,
but some are devoid of mordenite. A central filling of white calcite,
seen as rhombic cleavage surfaces up to 150 mm across, is present in a small number of the
mordenite-filled vesicles, and similar coarsely crystalline calcite
is a conspicuous constituent of the filling of the vesicles that are devoid of
mordenite, but contain prehnite
(JRS 23.86-90).
The Nelly James Mine, Miller Canyon, Miller Peak, Cochise County, Arizona, USA, is a former small surface
lead, copper,
zinc, gold and
silver mine located at an altitude of 7250 feet. Mineralisation is a vein deposit
Mindat).
The mine is now famous for fluorescent minerals collected from the dumps, including
calcite (fluoresces red),
hydrozincite (sky blue),
powellite (creamy-yellow),
smithsonite (crimson red),
sphalerite (yellow-orange) and
willemite (green).
Calcite is one of the most common minerals at the mine and is dominantly associated with
willemite. The calcite is typically massive and white in daylight,
turning tan or brown where the contained manganese has oxidised. Under
shortwave UV light the fluorescent response is usually a bright orange-red, but pinkish-red is also present. In some
specimens the calcite fluoresces a deeper red colour. Secondary
crosscutting veinlets of calcite may fluoresce a different shade of red than the massive
primary calcite. Under longwave UV light the response is a
weaker pink to pale red colour. Under medium range UV light the response is a weak red colour. The calcite also
exhibits a very brief sustained luminescence (phosphorescence) upon removal of the shortwave UV source
(R&M 97.1.48-56).
At the Camp Verde district, Yavapai county, Arizona, USA, calcite pseudomorphs
after glauberite have been found
(KL p155, R&M 87.1.18).
At the Copper Falls Mine, Copper Falls, Keweenaw county, Michigan, USA, mineralisation occurs primarily in hydrothermal veins
cutting preexisting lavas and as amygdules in the Ashbed flow.
Copper Falls has produced some exceptional calcite crystals. Copper inclusions in
calcite were noted as early as 1850. Perhaps the finest is a gem-quality calcite crystal resting on a matrix of
native copper which is now housed at the A E Seaman Mineral Museum
(MinRec 54.1.95-105).
The Central Mine, Central, Keweenaw county, Michigan, USA, initially targeted a series of sub-parallel mineralised
fissure veins where the most copper-rich portion of the vein was close to the
base of the main greenstone flow.
The Central mine has produced some outstanding crystallised calcite specimens, including beautifully transparent
and morphologically complex calcite crystals coloured by minute inclusions of native
copper. Another unique style of calcite specimen found here shows gemmy
crystals, typically scalenohedral, with dark red to brown hematite inclusions
forming phantoms
(MinRec 54.1.53-81).
The Cliff Mine, Phoenix, Keweenaw county, Michigan, USA, is situated at the base of a roughly 70-metre
basalt cliff. A curious feature of the impressive thickness of the
greenstone flow here is that it contains zones of “pegmatoid”: areas
where
slow cooling in the core of the lava flow allowed for large feldspar crystals
exceeding 1 cm to grow. Such features are normally only observed in intrusive igneous rocks and are almost unheard of
in basalt flows.
The Cliff mine primarily exploited rich copper mineralisation in the Cliff
fissure (vein). Although mineralised with copper to some extent along its
entire length, the part of the vein just below the greenstone flow
carried the richest copper mineralisation by far. A significant amount of the
copper recovered at the Cliff mine came from amygdaloids in the tops of 13
basalt flows which were cut by the Cliff vein. The discovery and mining
of this vein proved that the veins were the source of the large masses of float
copper that were already well known, and proved that the
primary ore mineral in the district was native
copper, not sulphides, as had been suspected earlier.
Calcite is a common vein-filling mineral as massive white material with prominent rhombohedral cleavage.
Crystals occurring in vugs are scalenohedral, less commonly rhombohedral. Calcite crystals are sometimes white
and opaque, but are more commonly colourless or pale yellow and transparent.
Copper inclusions in calcite are not uncommon, but the Cliff mine is not
a particularly important locality for Michigan’s highly sought-after
copper-in-calcite specimens
(MinRec 54.1.25-49).
At Joplin, Missouri, USA, hemimorphite
pseudomorphs after calcite have been found
(KL p225).
At Cookes Peak mining district, Luna county, New Mexico, USA, calcite is associated with
aragonite in cave-like formations, and it is also very common in cavities
with ore minerals and fluorite
(R&M 94.3.226).
At The Dafoe Property, Pierrepont, St Lawrence county, New York, USA,
calcite is associated with late stage quartz,
allanite-(Ce)
and occasionally hematite
(R&M 94.5.452-455).
At the Purple Diopside Mound, Rose Road, Pitcairn, St. Lawrence county, New York, USA, calcite, as a
secondary coating on various minerals, fluoresces a
greenish white under both long wave and short wave UV. The calcite in
marble is not fluorescent
(R&M 97.5.442).
At the Suever Stone Company quarry, Delphos, Van Wert county, Ohio, USA, calcite occurred as crystals and pocket fillings. Multiple
forms of calcite were encountered, including the rhombohedron, scalenohedral (dogtooth) crystals and blunt tapered crystals. The
rhombohedra are frequently truncated by the pinacoid {001}. This is rare for calcite occurrences in Ohio in general, but it is typical
of crystals from other oil-saturated strata in the state. Some of the calcite is quite fluorescent under longwave ultraviolet light;
deposits of this calcite seem to be late-stage coatings, sometimes on surfaces of existing calcite crystals; levels of
fluorescence range from pink to brilliant red. Earlier-formed calcite does not fluoresce
(R&M 95.6.502-505).
Some calcite from the lower level shows saddle-shaped junctions between crystals that are crystallographically continuous with
the crystal they abut. Fluorite and pyrite also occur with
similar unusual features. All of these unusual mineral examples have one thing in common; they were found in oil-saturated pockets. Petroleum
is often seen trapped in calcite crystals, and its presence seems to be linked to the "saddles", but the mechanism for their formation
is not known
(R&M 95.6.512-514).
At the Mid-Continent mine, Picher, Oklahoma, USA, a gypsum
pseudomorph after calcite has been found with
melanterite on sphalerite
(KL p189).
At the Luck Leesburg Plant, Leesburg, Loudoun county, Virginia, USA, calcite is ubiquitous and is most
commonly seen as tiny white crystals scattered on apophyllite or
prehnite
(R&M 98.2.124-125).
Alteration
Calcite and aragonite are precipitated according to the following
reactions:
Carbon dioxide in the atmosphere is dissolved in rainwater forming weak carbonic acid:
H2O + CO2 → H2CO3
Carbonic acid dissolves limestone forming calcium bicarbonate
H2CO3 + CaCO3 → Ca(HCO3)2
This solution percolates into caves
where calcium carbonate may be precipitated as calcite with the release of liquid water and gaseous carbon dioxide:
Ca(HCO3)2 ⇆ CaCO3 (solid) + H2O
(liquid) + CO2 (gas)
(R&M 91-4:329)
The net effect of these changes could be written as the reversible reaction
CaCO3 (solid) + H2CO3 (in solution) ⇌ Ca2+ +
2(HCO3)-
The forward reaction, solution of calcium carbonate, occurs in acid environments, and the reverse reaction, precipitation
of calcium carbonate, occurs in strongly basic (alkaline) environments.
(KB p62)
aegirine, epidote and CO2 to
albite, hematite,
quartz, calcite and H2O
4NaFe3+Si2O6 +
2Ca2(Al2Fe3+[Si2O7](SiO4)O(OH) + 4CO2
→ 4Na(AlSi3O8) + 3Fe2O3 + 2SiO2 + 4CaCO3 +
H2O
(DHZ 2A p511)
åkermanite and CO2 to diopside
and calcite
Ca2MgSi2O7 +
CO2 ⇌ CaMgSi2O6 + CaCO3
The maximum stability limit of åkermanite in the presence of excess CO2 is about 6 kbar. Below that
pressure, at relatively lower temperatures, åkermanite reacts with CO2 to form
diopside and calcite
according to the reaction:
(JVW p144)
albite, chlorite and calcite to
Ca, Mg-rich jadeite,
Al-rich glaucophane,
quartz, CO2 and H2O
8Na(AlSi3O8) +
(Mg4.0Fe2.0)(AlSi3O10)(OH)8 +
CaCO3 →
5(Na0.8Ca0.2)(Mg0.2Al0.8Si2)6 +
2Na2(Mg3Al2)(Al0.5Si7.5)O22(OH)2 +
2SiO2 + CO2 + 2H2O
In low to intermediate metamorphism jadeite-glaucophane assemblages may arise from reactions such as the one above.
(DHZ 2A p475)
calcium amphibole, calcite and quartz to
diopside-hedenbergite,
anorthite, CO2 and H2O
Ca2(Mg,Fe2+)3Al4Si6O22(OH)2 +
3CaCO3 + 4SiO2 = 3Ca(Fe,Mg)Si2O6 +
2Ca(Al2Si2O8) + 3CO2 + H2O
Diopside-hedenbergite occurs
commonly in regionally metamorphosed calcium-rich sediments and basic igneous rocks
belonging to the higher grades of the amphibolite facies, where it may
form according to the above reaction.
(DHZ 2A p272)
amphibole, chlorite,
paragonite, ilmenite,
quartz and calcite to garnet,
omphacite, rutile, H2O
and CO2
NaCa2(Fe2Mg3)(AlSi7)O22(OH)2 +
Mg5Al(AlSi3O10)(OH)8 +
3NaAl2(Si3Al)O10(OH)2 + 4Fe2+Ti4+O3 +
9SiO2 + 4CaCO3 →
2(CaMg2Fe3)Al4(SiO4)6 +
4NaCaMgAl(Si2O6)2 + 4TiO2 + 8H2O +
4CO2
In low-grade rocks relatively rich in calcite the garnet-omphacite association may be due to reactions such as
the above.
(DHZ 2A p453)
anorthite to calcite and
kaolinite in the early Earth's atmosphere
CO2 + H2O + anorthite → calcite +
kaolinite
CO2 + 2H2O + CaAl2Si2O8 → CaCO3 +
Al2Si2O5(OH)4
(JVW p634)
anorthite, H2O and CO2 ⇌
kaolinite and
calcite
2CaAl2 Si2O8 + 4H2O + 2CO2 ⇌
Al4Si4O10(OH)8 + 2CaCO3
Calcite is found as a low-temperature, late-stage alteraation product according to the above reaction.
(DHZ 5B p128)
anorthite and calcite to
meionite (scapolite series)
3Ca(Al2Si2O8) + CaCO3 ⇌
Ca4Al6O24(CO3)
This reaction occurs in the presence of a high CO2 pressure in an environment deficient in (Al+Na+K).
(DHZ 4 p331)
antigorite and
calcite to
forsterite,
diopside, CO2 and H2O
3Mg3Si2O5(OH)4 + CaCO3 →
4Mg2SiO4 + CaMgSi2O6 + CO2 +6 H2O
This reaction has been found to occur in antigorite schist at about 3 kbar
pressure and 400 to 500oC (greenschist facies).
(DHZ 1A p263)
aragonite or calcite and Mg2+
(from Mg-rich fluid) to dolomite and Ca2+
2CaCO3 + Mg2+ ⇌ CaMg(CO3)2 + Ca2+
augite and CO2 to
enstatite-ferrosilite,
calcite and quartz
Ca(Mg,Fe)Si2O6 + CO2 → (Mg,Fe)SiO3 + CaCO3 +
SiO2
(DHZ 2A p384)
bustamite, tephroite and calcite to
glaucochroite and CO2
CaMn2+Si2O6 + Mn2+2(SiO4) + 2CaCO3
⇌ 3CaMn2+(SiO4) + 2CO2
(DHZ 1A p348)
calcite, Ba2+, H2S and O2 to baryte,
Ca2+, CO2 and H2O
CaCO3 + Ba2+ + H2S + 2O2 = BaSO4 + Ca2+ +
CO2 and H2O
Baryte may be precipitated by the action of ore fluid and groundwater on calcite.
(DHZ 5B p16)
calcite, Fe2+ and Mg2+ to ankerite and Ca2+
4CaCO3 + Fe2+ + Mg2+ =
2Ca(Mg
Ankerite is believed to be formed from calcite hydrothermally according to the above reaction.
(DHZ 5B p228)
calcite, hematite and
quartz to andradite and
CO2
3CaCO3 + Fe2O3 + 3SiO2 →
Ca3Fe3+2Si3O12 + 3CO2
calcium amphibole, calcite and
quartz to
diopside-hedenbergite,
anorthite, CO2 and H2O
Ca2(Mg,Fe2+)3Al4Si6O22(OH)2 +
3CaCO3 + 4SiO2 = 3Ca(Fe,Mg)Si2O6 +
2Ca(Al2Si2O8) + 3CO2 + H2O
Diopside-hedenbergite occurs commonly in regionally metamorphosed calcium-rich sediments and basic igneous rocks
belonging to the higher grades of the amphibolite facies, where it may form according to the above reaction.
(DHZ 2A p272)
dellaite and calcite to
spurrite and H2O
2Ca6(Si2O7)(SiO4)(OH)2 + 3CaCO3 ⇌
3Ca5(SiO4)2(CO3) + 2H2O
Higher temperatures favour the forward reaction
(MM 34.1.1-16).
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 dolomite to
forsterite,
calcite and CO2
CaMgSi2O6 + 3CaMg(CO3)2 →
2Mg2SiO4 + 4CaCO3 + 2CO2
This is a high-grade metamorphic change occurring at temperature in excess of 600oC.
(MOM, DHZ 5B p213)
diopside, dolomite, CO2 and
H2O to actinolite 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)
diopside, dolomite and
H2O ⇌ hydroxylclinohumite,
calcite and CO2
2CaMgSi2O6 + 7CaMg(CO3)2 + H2O ⇌
Mg9(SiO4)4(OH)2 + 9CaCO3 + 5CO2
In the nodular dolomites, clinohumite
associated with calcite occurs in a narrow zone in the central parts of the
nodules due to the above reaction
(DHZ 1A p264).
diopside, forsterite and
calcite to monticellite and CO2
CaMgSi2O6 + Mg2SiO4 + 2CaCO3 → 3CaMgSiO4 +
2CO2
This reaction requires a high temperature.
(DHZ 2A p271)
diopside-hedenbergite and
CO2 to enstatite-
ferrosilite, calcite and quartz
Ca(Mg,Fe)Si2O6 + CO2 → (Mg,Fe2+)SiO3 + CaCO3 +
SiO2
(DHZ 2A p136)
dolomite and
chert to talc and
calcite
3CaMg(CO3)2 + 4SiO2 + H2O →
Mg3Si4O10(OH)2 + 3CaCO3 + 3CO2
Metamorphism of siliceous carbonate rocks causes the formation of hydrous phases such as
talc and
tremolite.
(DHZ 5B p127)
This is a very low-grade metamorphic reaction occurring at temperature between about 150oC and
250oC.
(MOM)
dolomite and muscovite to
phlogopite,
calcite, CO2 and Al2O3
3CaMg(CO3)2 + KAl2(AlSi3O10)(OH)2
→ KMg3(AlSi3O10)(OH)2 + 3CaCO3 + 3CO2
+ Al2O3
The excess alumina may be used to form spinel
(DHZ 3 p51)
dolomite, K-feldspar and H2O
to
phlogopite, calcite and
CO2
3CaMg(CO3)2 + KAlSi3O8 + H2O =
KMg3AlSi3O10(OH)2 + 3CaCO3 + 3CO2
In the presence of Al and K the metamorphism of dolomite leads to the formation of
phlogopite according
to the above equation.
(DHZ 5B p213)
dolomite and
quartz to
forsterite,
calcite and CO2
2CaMg(CO3)2 + SiO2 → Mg2SiO4 + 2CaCO3
+ 2CO2
In siliceous dolostone dolomite and quartz may react to form either
diopside
or forsterite, with diopside forming at a lower temperature
than forsterite.
(DHZ 2A p270, 1A p264)
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
Dolomite can be metamorphosed to talc and
calcite, then at higher temperatures the talc and calcite react to
form tremolite. In turn tremolite reacts with dolomite
to form forsterite, according to the above equation.
(DHZ 5B p213)
enstatite and calcite to forsterite,
diopside and CO2
3Mg2Si2O6 + 2CaCO3 ⇌ 2Mg2SiO4 +
2CaMgSi2O6 + 2CO2
enstatite is uncommon in the more calcareous
hornfels due to reactions such as the above.
(DHZ 2A p135)
enstatite, calcite and quartz to
diopside and CO2
3Mg2Si2O6 + 2CaCO3 + 2SiO2 ⇌ +
2CaMgSi2O6 + 2CO2
enstatite is uncommon in the more calcareous
hornfels due to reactions such as the above.
(DHZ 2A p135)
ferro-actinolite, calcite and quartz
to
hedenbergite, CO2 and H2O
Ca2Fe2+5Si8O22(OH)2 + 3CaCO3 +
2SiO2 ⇌ 5CaFe2+Si2O6 + 3CO2 + H2O
In some calc-silicate rocks hedenbergite is the product of metamorphism of
iron-rich sediments, according to the above reaction, probably due to the instability of ferro-actinolite with
rising temperature.
(DHZ 2A.273)
forsterite, calcite and quartz to
diopside and CO2
Mg2SiO4 + 2CaCO3 + 3SiO2 → 2CaMgSi2O6 +
2CO2
In high temperature environments with excess SiO2 diopside may form accoring
to the above reaction.
(DHZ 2A.271)
forsterite,
calcite and quartz to
monticellite and CO2
Mg2SiO4 + 2CaCO3 + SiO2 → 2CaMg(SiO4) + 2CO2
forsterite,
diopside and calcite to
monticellite and CO2
Mg2SiO4 + CaMgSi2O6 + 2 CaCO3 ⇌ 3CaMg(SiO4) +
2 CO2
This reaction occurs during contact metamorphism of magnesian
limestone.
(DHZ 1A p353)
forsterite and
dolomite to calcite and
hydroxylclinohumite
4Mg2SiO4 + CaMg(CO3)2 + H2O →
Mg9(SiO4)4(OH)2 + CaCO3 + CO2
This is probably the reaction responsible for a forsterite-
clinohumite assemblage in silica-rich
dolomite in the aureole of the Alta
granodiorite in Utah, USA
(DHZ 1A p264).
forsterite, dolomite and H2O
to calcite, hydroxylclinohumite
and CO2
4Mg2SiO4 + CaMg(CO3)2 + H2O →
Mg9(SiO4)4(OH)2 +CaCO3 + CO2
A forsterite-clinohumite assemblage in the silica-rich
dolomite in the aureole of the Alta
granodiorite in Utah, USA, is
probably due to the above reaction.
(DHZ 1A.264)
grossular, diopside,
monticellite, calcite and H2O to
vesuvianite, quartz and CO2
10Ca3Al2(SiO4)3 + 3CaMgSi2O6 + 3CaMg(SiO4)
+ 2CaCO3 + 8H2O ⇌
2Ca19Al10Mg3(SiO4)10
(Si2O2)4O2(OH)8 + 3SiO2 + 2CO2
A common association in calc-silicate metamorphism can be represented by the above equation. Vesuvianite stability
will tend to increase with increasing water and decrease as the activity of CO2 rises.
(DHZ 1A.714)
hematite,
wüstite, quartz and
calcite to andradite, hedenbergite
magnetite and
CO2
2Fe2O3 + 2FeO + 5SiO2 + 4CaCO3 →
Ca3Fe3+2(SiO4)3 + CaFe2+Si2O6
+Fe2+Fe3+2O4
+4CO2
hornblende, calcite and quartz to
Fe-rich diopside, anorthite,
CO2 and H2O
Ca2(Mg,Fe2+)3(Al4Si6)O22(OH)2 +
3CaCO3 + 4SiO2 = 3Ca(Mg,Fe2+)Si2O6 +
2Ca(Al2Si2O8) + 3CO2 + H2O
Fe-rich diopside occurs commonly in
regionally metamorphosed calcium-rich sediments and basic igneous rocks
belonging to the higher grades of the amphibolite facies. The
above reaction is typical.
(DHZ 2A.272)
kaolinite,
dolomite,
quartz and H2O to chlorite,
calcite and CO2
Al2Si2O5(OH)4 + 5CaMg(CO3)2 + SiO2
+ 2H2O ⇌ Mg5Al(AlSi3O10)(OH)8 + 5CaCO3 +
5CO2
Chlorite often forms in this way from reactions between clay minerals such as kaolinite and
carbonates such as
dolomite.
(KB p377)
laumontite and calcite to prehnite,
quartz, H2O and CO2
CaAl2Si4O12.4H2O + CaCO3 →
Ca2Al(Si3Al)O10(OH)2 + SiO2 + 3H2O + CO2
Prehnite and pumpellyite form from the Ca zeolites in the presence of calcite, as in the above equation.
(DHZ 5B.127)
meionite (scapolite series) and augite to
garnet, calcite and quartz
Ca4Al6O24(CO3) + 3Ca(Mg,Fe2+)Si2O6
⇌ 3Ca2(Mg,Fe2+)Al2(SiO4)3 + CaCO3 +
3SiO2
(DHZ 4.334)
meionite (scapolite series), calcite and quartz to
grossular and CO2
Ca4Al6O24(CO3) + 5CaCO3 + 3SiO2 ⇌
3Ca3Al2(SiO4)3 + 6CO2
(DHZ 4.334)
monticellite and CO2 to
åkermanite, forsterite and
calcite
3CaMgSiO4 + CO2 ⇌ Ca2MgSi27 +
Mg2O7 + CaCO3
At 4.3 kbar pressure the equilibrium temperature is about 890oC
(granulite facies).
(DHZ 1A.357)
monticellite and
spurrite to
merwinite and
calcite
2CaMg(SiO4) + Ca5(SiO4)2(CO3) ⇌
2Ca3Mg(SiO4)2 + CaCO3
phlogopite, calcite and silica to
diopside, K-feldspar, H2O
and CO2
KMg3(AlSi3O10)(OH)2 + 3CaCO3 + 6SiO2 =
3CaMgSi2O6 + K(AlSi3O8) + H2O + 3CO2
In reaction zones between interbedded carbonate and pelitic beds of the
calc-mica schist,
phlogopite may alter
according to the above reaction.
(DHZ 2A.272)
The association of phlogopite and calcite is stable only in the absence of
excess silica.
(DHZ 3.51)
quartz and calcite to wollastonite
and CO2
3SiO2 + 3CaCO3 ⇌ Ca3Si3O9 +
3CO2 (gaseous)
This is a contact metamorphic change occurring at temperatures from about
600°C such as in the immediate border zone of an igneous intrusion into limestone.
(MOM p486, KB p417)
High pressure inhibits the forward reaction by suppressing the formation of gaseous CO2.
(KB p18)
At 10 kbar pressure the equilibrium temperature is about 1,070oC (granulite facies).
(SERC)
talc and calcite to dolomite
and quartz
talc + calcite + CO2 ⇌
dolomite +
quartz + H2O
Mg3Si4O10(OH)2 + 3CaCO3 + 3CO2 ⇌
3CaMg(CO3)2 + 4SiO2 + H2O
(JVW p144)
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.127, 213)
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.249)
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.264)
tremolite, dolomite and
H2O ⇆
hydroxylclinohumite, calcite
and CO2
Ca2Mg5Si8O22(OH)2 + 13CaMg(CO3)2
+ H2O ⇆ 2Mg9(SiO4)4(OH)2 + 15CaCO3 + 11CO2
(DHZ 1A).
wollastonite and calcite to
tilleyite and CO2
2CaSiO3 + 3CaCO3 ⇌ Ca5Si2O7(CO3)2+ CO2
Higher temperatures favour the forward reaction
(MM 34.1.1-16).
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