Formula: Cu5Si6O17.7H2O
Unclassified silicate
Crystal system: Monoclinic
Specific gravity: 2.72 measured, 2.54 calculated
Hardness: 2
Streak: Light green
Colour: Green to blue-green
Solubility: Easily soluble in cold, dilute nitric or hydrochloric acid
Common impurities: Mn,Mg,Ca
Environments:
Localities
At the type locality, the Christmas Mine, Christmas, Banner Mining District, Gila County, Arizona, USA,
gilalite is a retrograde metamorphic or mesogene
mineral formed at the expense of a prograde calc-silicate and
sulphide assemblage, commonly encrusting fractures in
garnet-diopside
skarn. It is also found filling cracks or interstices in
diopside grains. Associated minerals include
kinoite, apachite,
stringhamite, junitoite,
clinohedrite, xonotlite,
diopside, apophyllite,
calcite and tobermorite
(HOM).
Gilalite from the Christmas Mine - Image
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