adularia

[aj-uh-lair-ee-uh]
noun Mineralogy.
a sometimes opalescent variety of orthoclase formed at a low temperature.

Origin:
1790–1800; < Italian < French adulaire, named after Adula a mountain group in Switzerland; see -ary

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World English Dictionary
adularia (ˌædjʊˈlɛərɪə)
 
n
a white or colourless glassy variety of orthoclase in the form of prismatic crystals. It occurs in metamorphic rocks and is a minor gemstone. Formula: KAlSi3O8
 
[C18: via Italian from French adulaire, after Adula, a group of mountains in Switzerland]

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Encyclopedia Britannica
Encyclopedia

adularia

a feldspar mineral and potassium aluminosilicate (KAlSi3O8). 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.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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Example sentences
Adularia and chlorite are present in veins cutting certain shales.
Adularia is locally altered to sericite, making the rock highly friable.
Source of the placers interpreted as gold-silver-adularia-quartz veins.
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