Hyalophane - Encyclopedia

    Class : Silicates
    Subclass : Tectosilicates
    Crystal system : Monoclinic
    Chemistry : (K,Ba)Al(Al,Si)3O8
    Rarity : Uncommon


Hyalophane is a rare mineral from the feldspar group in which it forms two series with orthoclase and celsian. It is an accessory mineral of manganiferous metamorphic rocks and manganiferous pyrometasomatic deposits, which is also found in carbonate rocks and Alpine clefts. Its name comes from the Greek hualos (glass) and phanos (shiny) or phainein (to appear), in allusion to its transparent and shiny appearance, similar to glass. Hyalophane forms crystals similar to those of adularia or orthoclase, frequently rhombohedral in appearance, commonly twinned like orthoclase, which can reach 20 cm. Hyalophane is colorless to whitish, straw yellow, sometimes pink to orange-yellow, exceptionally yellow-brown.


Main photo : Hyalophane from Zagradski Potok Mine, Bosnia-Herzegovina © Jordy Fabre

Hyalophane in the World

The Busovaca deposit (Bosnia-Herzegovina) produced the most beautiful known crystals : complex twinned specimens exceeding 15 cm. The dolomite of Lengenbach (Switzerland) has produced beautiful crystals, as have the calcite veins of the Slyudyanka river near Irkutsk (Russia) and the metamorphic manganese deposit of Langban (Sweden).

Right photo : Hyalophane from Lengenbach, Valais, Switzerland © Stephan Wolfsried

Hyalophane in France

In France, hyalophane is known in Plan de Labasse (Hautes-Pyrénées).

Twinning

Twins are common for this mineral species.

Fakes and treatments

No fakes recorded for this mineral species.



Hardness : 6 to 6.5
Density : 2.54 to 2.57
Fracture : Irregular
Streak : White


TP : Translucent to transparent
RI : 1.542 to 1.547
Birefringence : 0.005
Optical character : Biaxial -
Pleochroism : None
Fluorescence : Pink


Solubility : Insoluble

Magnetism : NoneRadioactivity : None

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