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Blue Gilalite cystals
Category Silicate mineral
(repeating unit)
Strunz classification 9.HE.05
Crystal system Monoclinic
Unknown space group
Unit cell a = 13.38, b = 19.16
c = 9.026 [Å]; β ≈ 90°; Z = 4
Formula mass 884.3 g/mol
Color Blue green, green
Crystal habit Raidiating fibrous in spherules
Tenacity Waxy or gummy
Mohs scale hardness 2
Luster Nonmetallic
Streak Light green
Diaphaneity Translucent
Specific gravity 2.72
Optical properties Biaxial (-)
Refractive index nα= 1.560 nβ=1.635 nΎ= 1.635
Birefringence δ = 0.075
References [1][2][3]

Gilalite is a copper silicate mineral with chemical composition of Cu5Si6O17·7(H2O).[3]

It occurs as a retrograde metamorphic phase in a calc-silicate and sulfde skarn deposit. It occurs as fracture fillings and incrustations associated with diopside crystals.[2] It is commonly found in the form of spherules of radial fibers.

Gilalite inclusions within a quartz crystal from Juazeiro do Norte, Ceara State, Brazil (size: 7.1 x 4.7 x 2.7 cm)

It was first described for an occurrence in the Christmas porphyry copper mine in Gila County, Arizona in 1980 along with the mineral apachite.[4] It derives its name from this locality. It has also been reported from the Goodsprings District, Clark County, Nevada; Juazeiro do Norte, Ceara State, Brazil and a slag area in Lavrion District, Attica, Greece.[3]


  1. ^ gilalite - Wolfram Alpha
  2. ^ a b Handbook of Mineralogy
  3. ^ a b c Gilalite: Gilalite mineral information,
  4. ^ F.P. Cesbron and S.A. Williams; March 1980;"Apachite and gilalite, two new copper silicates from Christmas, Arizona" Mineralogical Magazine, Vol. 43, pp. 639-41