alum stone

alunite

[al-yuh-nahyt]
noun
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-uhm-stohn] .


Origin:
1865–70; < French alun (< Latin alūmen alum1) + -ite1

Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
Cite This Source Link To alum stone
Collins
World English Dictionary
alunite (ˈæljʊˌnaɪt)
 
n
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
 
[C19: from French alun alum (from Latin alūmen) + -ite1]

Collins English Dictionary - Complete & Unabridged 10th Edition
2009 © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009
Cite This Source
Encyclopedia Britannica
Encyclopedia

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)

Learn more about alum stone with a free trial on Britannica.com.

Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
Cite This Source
Copyright © 2014 Dictionary.com, LLC. All rights reserved.
  • Please Login or Sign Up to use the Recent Searches feature