Call number:
Framework Silicates
D69 (11)
D69 (11)
Classification:
Framework Silicates (Feldspars Group)
Name:
Orthoclase var. Adularia
Translated title:
Orthoclase var. Adularia
Place of origin:
St. Gotthard, Switzerland
Depositional environment:
Intrusive and extrusive igneous, and metamorphic rocks. A more ordered low-temperature variety of Orthoclase, generally found in Alpine-type parageneses.
Description:
Intrusive and extrusive igneous, and metamorphic rocks. A more ordered low-temperature variety of Orthoclase, generally found in Alpine-type parageneses. It is a form of orthoclase which crystallizes at unusually low temperatures. It is found in the Adula Mountains of Switzerland.It commonly forms colourless, glassy, prismatic, twinned crystals in low-temperature veins of felsic plutonic rocks and in cavities in crystalline schists. Typical occurrences include the schists of the Alps. Some adularia show an opalescent play of colours and are called moonstone.
Chemical formula:
KAlSi3O8
Crystal system:
Orthorhombic
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