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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.]
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
(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]
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014
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]
Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.