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A colorless to milky white mineral of the potassium feldspar group that forms from relatively low-temperature magmas and lacks structural homogeneity.
[Italian, from French adulaire, after Adula, a mountain group of southeast Switzerland.]
(Minerals) 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]
ad•u•lar•i•a(ˌædʒ əˈlɛər i ə)
n., pl. -lar•i•as.
a sometimes opalescent variety of orthoclase formed at a low temperature.
[1790–1800; < Italian < French adulaire, after Adula a mountain group in Switzerland; see -ary]