Mineralpedia Details for Gilalite

Named for the type locality in the Christmas mine in Gila County, Arizona in the United States. Gilalite is a rare mineral that can only be found in Arizona and Nevada in the USA, in Greece at Laurion, and in Brazil. At its type locality, Gilalite is “a retrograde metamorphic or megogene mineral formed at the expense of a prograde calc-silicate and sulfide assemblage, in tactites commonly incrusting fractures, [and] also filling cracks or interstices in diopside grains.”

Ref. Handbook of Mineralogy, Anthony et al (1995) and MSA at http://www.handbookofmineralogy.org/pdfs/gilalite.pdf

Formula

Cu₅Si₆O₁₇·7H₂O 

Crystal System

Monoclinic 

Crystal Habit

Spherical, Radial, Fibrous 

Color

blue green, green 

Streak

light green 

Class

Monoclinic 

Hardness

2 

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Mindat

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Light green spheroidal crystals to about 0.75mm.

Dozens of pastel green, smooth bead-like crystals to about 0.75mm. 

Green spherical crystals to 0.3mm in bunches with Stringhamite.