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Formula: Ca12Mg4Al(CO3)5(BO3)3(SiO4)4.H2O
Compound carbonate, forms a solid solution with sakhaite
Crystal System: Trigonal
Specific gravity: 2.96 measured, 3.00 calculated
Streak: White
Colour: White, tannish brown
Solubility: Dissolves with effervescence in acetic or hydrochloric acid
Common impurities: TR,Ce,Fe,Mn,Sr,F,Cl
Environments
Volcanic igneous environments
Metamorphic environments
Harkerite is a high-temperature mineral that occurs in skarn in
dolomitic limestone at the
contact with granite
(Webmin, Mindat). Associated minerals include calcite,
chalcocite, monticellite,
diopside, magnetite,
vesuvianite, cuspidine and
phlogopite
(HOM, Mindat).
Localities
At the Alban Hills, Metropolitan City of Rome Capital, Lazio, Italy, harkerite occurs in volcanic ejecta
(HOM).
At the type locality, Camas Malag, Torrin, Broadford, Isle of Skye, Eilean á Chèo, Highland, Scotland, UK, harkerite occurs
in skarn containing monticellite and
calcite, and accessory bornite,
chalcocite, magnetite and
diopside, at the contact of
dolomitic limestone with
granite (AM 37.359). The harkerite is associated very intimately
with calcite, which is a product of its alteration
(AM 62.263-272).
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