Alunite, or alumstone, is a mineral that was first observed in the 15th century in Monti della Tolfa, north to Rome, where it was mined for the manufacture of alum. First called "aluminilite" by J.C. Delametherie in 1707, this name was contracted by François Beudant in 1824 to alunite.

Distinct crystals of alunite are rarely found in cavities in the massive material. Alunite crystallizes in the hexagonal system with crystals forming trigonal pyramids that resemble rhombohedra with interfacial angles of 90 50', so that they resemble cubes in appearance. Minute glistening crystals have also been found loose in cavities in altered rhyolite. Alunite varies in color from white to yellow gray. The hardness is 4 and the specific gravity is between 2.6 and 2.8. The mineral is a hydrated aluminium potassium sulfate, KAl3(SO4)2(OH)6. Sodium substitutes for potassium and when high in sodium it is called natroalunite. It is insoluble in water or weak acids, but soluble in sulfuric acid. Jarosite is an iron analogue in which Fe3+ replaces the aluminium. It occurs as a secondary mineral on iron sulfate ores.

Alunite occurs as veins and replacement masses in trachyte, rhyolite, and similar potassium rich volcanic rocks It is formed by the action of sulfuric acid bearing solutions on these rocks during the oxidation and leaching of metal sulfide deposits. Alunite also is found near volcanic fumaroles. The white, finely granular masses closely resemble finely granular limestone, dolomite, anhydrite, and magnesite in appearance. The more compact kinds from Hungary are so hard and tough that they have been used for millstones.

Historically extensive deposits were mined in Tuscany and Hungary, and at Bulahdelah, Australia. Currently found at Tolfa, Italy. In the United States it is found in the San Juan district of Colorado; Goldfield, Nevada; the ghost town of Alunite, Utah near Marysvale; and Red Mountain in Patagonia, Arizona. The Arizona occurrence lies appropriately above a canyon named "Alum Gulch". Alunite is mined as an ore of both potassium and aluminium at Marysvale. Some of the ore deposits were located by airborne and satellite multispectral imaging.


*cite book|last=Hurlbut|first=Cornelius S.|year=1966 |title=Dana's Manual of Mineralogy|edition=17th ed.|id=ISBN 0-471-03288-3
*cite book|last=Hurlbut|first=Cornelius S.|coauthors =Cornelis Klein|year=1985|title=Manual of Mineralogy|edition=20th ed.|id=ISBN 0-471-80580-7

External links

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  • Alunite — Alunite[1] Catégorie VII : sulfates, sélénates tellurates, chromates, molybdates, tungstates[2] …   Wikipédia en Français

  • alunite — [ alynit ] n. f. • 1824; de alun ♦ Sulfate basique double hydraté d aluminium et de potassium que l on trouve dans la nature, utilisé pour la production d alun et de sulfate d aluminium. ● alunite nom féminin (de alun) Sulfate d aluminium naturel …   Encyclopédie Universelle

  • Alunite — Al u*nite, n. (Min.) Alum stone. [1913 Webster] …   The Collaborative International Dictionary of English

  • alunite — [al′yo͞o nīt΄, al′yənīt΄] n. [Fr < alun < L alumen, ALUM1] a semihard, hydrous mineral, KAl3 (SO4) 2 (OH) 6, used to produce alum …   English World dictionary

  • alunite — a·lu·nì·te s.f. TS mineral. minerale di colore bianco o rossiccio costituito da solfato idrato di alluminio e potassio {{line}} {{/line}} DATA: 1845. ETIMO: dal fr. alunite, der. di alun allume …   Dizionario italiano

  • alunite — alūnitas statusas T sritis chemija apibrėžtis Mineralas. formulė KAl₃[(OH)₆|(SO₄)₂] atitikmenys: angl. alunite rus. алунит …   Chemijos terminų aiškinamasis žodynas

  • Alunite, Utah — Alunite (Pron en|ˈæljuːnаɪt) is a ghost town located some convert|5|mi south of Marysvale, near the mouth of Cottonwood Canyon in Piute County, Utah, United States. A small but important mining town during World War I, Alunite was inhabited about …   Wikipedia

  • alunite — noun Etymology: French, from alun alum Date: 1868 a mineral that consists of a hydrous potassium aluminum sulfate and occurs in massive form or in rhombohedral crystals …   New Collegiate Dictionary

  • alunite — /al yeuh nuyt /, n. a mineral, a hydrous sulfate of potassium and aluminum, KAl3(SO4)2(OH)6, commonly occurring in fine grained masses. Also called alumstone /al euhm stohn /. [1865 70; < F alun ( < L alumen ALUM1) + ITE1] * * * ▪ mineral also… …   Universalium

  • alunite — noun A gray, water soluble mineral, potassium aluminium sulphate; the natural source of alum, KAl(SO)(OH) …   Wiktionary

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