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Formula: Ca2Al3[Si2O7][SiO4]O(OH)
Sorosilicate (Si2O7 groups) epidote group,
epidote supergroup
Crystal System: Monoclinic
Specific gravity: 3.3 to 3.4 measured, 3.23 calculated
Hardness: 7
Streak: Greyish white
Colour: Colourless, green, grey, light green, yellow-green, pink
Solubility: Insoluble in water, nitric and sulphuric acid; soluble in hydrochloric acid
Common impurities: Ti,Fe,Mn,Mg
Environments:
Metamorphic environments
Hydrothermal environments
Clinozoisite is a mineral of the amphibolite 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.
Clinozoisite is a primary silicate that occurs as pale
yellow grains associated with epidote,
chlorite and, in some cases, quartz
(AJM 22.1.35).
At the Dolgellau Gold-belt, Gwynedd, Wales, UK, clinozoisite occurs, together with
epidote,
quartz, calcite and
albite,
in alpine-fissure type assemblages at a number of localities. It forms acicular brownish crystals to 3 cm
(MW).
At Gellilydan, Gwynedd, Wales, UK, a number of alpine fissure-type veins were exposed in a road cutting, hosted in altered basic
intrusive
bodies. Buff crystals of clinozoisite up to several centimetres in length were abundant in some of the veins, in association
with quartz and calcite
(MW).
Alteration
calcium-iron amphibole and anorthite to
garnet (grossular and
almandine), clinozoisite and quartz
Ca2Fe3Si8O22(OH)2 + 6Ca(Al2Si2O8) ⇌
4/3Ca3Al2(SiO4)3 + 5/3Fe3Al2(SiO4)3 +
2Ca2Al3[SiO7][SiO4]O(OH) + 5SiO2
(MM 48.206)
amphibole, clinozoisite, chlorite,
albite, ilmenite and
quartz to garnet,
omphacite, rutile and H2O
NaCa2(Fe2Mg3)(AlSi7)O22(OH)2 +
2Ca2Al3[Si2o7][SiO4]O(OH) +
Mg5Al(AlSi3O10)(OH)8 + 3NaAlSi3O8 +
4Fe2+Ti4+O3 + 3SiO2 →
2(CaMg2Fe3)Al4(SiO4)6 +
4NaCaMgAl(Si2O6)2 + 4TiO2 + 6H2O
In low-grade rocks relatively poor in calcite the garnet -
omphacite association may be developed by the above reaction
(DHZ 2A p453).
lawsonite and jadeite to clinozoisite,
paragonite, quartz and H2O
4CaAl2(Si2O7)(OH)2.H2 + NaAlSi2O6
⇌ 2Ca2Al3[Si2O7][SiO4]O(OH) +
NaAl2(Si3Al)O10(OH)2 + SiO2 +6H2
Clinozoisite and paragonite may have been derived from
lawsonite by the above reaction
(DHZ 2A p477).
meionite (scapolite series) and H2O to clinozoisite and CO2
Ca4Al6O24(CO3) + H2O ⇌
2Ca2Al3[Si2O7][SiO4]O(OH) + CO2
(DHZ 4 p334)
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