[al-yuh-nahyt] 
| a mineral, a hydrous sulfate of potassium and aluminum, KAl3(SO4)2(OH)6, commonly occurring in fine-grained masses. |
| al·u·nite (āl'yə-nīt') n. A gray mineral, chiefly K2Al3(OH)6(SO4)3, used in making alum and fertilizer. [French, from alun, alum, from Latin alūmen.] |
alunite
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 alunite with a free trial on Britannica.com.
yəˌnaɪt