Sorosilicate (Si2O7 groups) epidote group
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
Clinozoisite is a mineral of the amphibolite facies.
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).
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
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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