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[al-yuh-nahyt] /ˈæl yəˌnaɪt/
a mineral, a hydrous sulfate of potassium and aluminum, KAl 3 (SO 4) 2 (OH) 6 , commonly occurring in fine-grained masses.
Also called alumstone
[al-uh m-stohn] /ˈæl əmˌstoʊn/ (Show IPA)
1865-70; < French alun (< Latin alūmen alum1) + -ite1 Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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Examples from the web for alunite
  • These hills are the site of major deposits of volcanogenic uranium and replacement alunite.
  • Further evidence for this is the presence of a mineral in the plume called alunite.
  • Intense alteration reduces host rock to alunite and clay.
  • Field examination showed the kaolinite and alunite may be in hydrothermally brecciated rock.
British Dictionary definitions for alunite


a white, grey, or reddish mineral consisting of hydrated aluminium sulphate. It occurs in volcanic igneous rocks and is a source of potassium and aluminium compounds. Formula: KAl3(SO4)2(OH)6
Word Origin
C19: from French alun alum (from Latin alūmen) + -ite1
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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Encyclopedia Article for alunite

alum stone

a widespread rock-forming sulfate mineral that occupies pockets or seams in volcanic rocks such as rhyolites, trachytes, and andesites, where it presumably formed through their chemical reaction with escaping sulfurous vapours. It has been used as a source of potash (during World War I) and as a source of alumina (during World War II); in Europe it was once used extensively to make potash alum, and it has been mined for this purpose since the 15th century. Large deposits exist near Beregovo, Ukraine; Almeria, Spain; and Bullah Delah in New South Wales, Australia. For chemical formula and physical properties, see sulfate mineral (table)

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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