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

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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]

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