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Chemical formula(K,Ba)[Al(Si,Al)Si2O8]
Molecular Weight302.06 gm
Colorcolorless, yellow, white, red
Crystal habitcrystalline - fine - occurs as well-formed fine sized crystals; massive - uniformly indistinguishable crystals forming large masses
Crystal systemmonoclinic
Twinningcommonly simple twins according to the Carlsbad, Manebach, or Baveno laws
Cleavage{001} perfect, {010} imperfect
Fracturebrittle - generally displayed by glasses and most non-metallic minerals
Mohs Scale hardness6 – 6½
Lustervitreous (glassy)
Refractive indexnα = 1.542, nβ = 1.545, nγ = 1.547
Optical Propertiesbiaxial (-)
Birefringenceδ = 0.005
References[1] [2] [3] [4]

Hyalophane or jaloallofane is a crystalline mineral with chemical formula (K,Ba)[Al(Si,Al)Si2O8] and a hardness of 6 – 6½. It is part of the feldspar group of tectosilicates, and is considered a Barium-rich Potassium feldspar.[5] Hyalophane comes from the Greek hyalos, meaning "glass", and phanos meaning "to appear".[4]

An occurrence of hyalophane was discovered in 1855 in Lengenbach Quarry, Imfield, in the municipality of Binn, Switzerland. The mineral is found predominantly in Europe, with occurrences in Switzerland, Australia, Bosnia, Germany, Japan, New Jersey, and the west coast of North America.[4]

Hyalophane has a monolinic crystallography, with cell properties a = 8.52Å, b = 12.95Å, c = 7.14Å and β = 116°. Optically, the material exhibits biaxial birefringence, with refractive index values of nα = 1.542, nβ = 1.545, and nγ = 1.547 and a maximum birefringence of δ = 0.005. It has weak dispersion and low surface relief.[1]


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This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Hyalophane". A list of authors is available in Wikipedia.
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