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ALUNITE, or ALUMSTONE

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Originally appearing in Volume V01, Page 773 of the 1911 Encyclopedia Britannica.
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ALUNITE, or ALUMSTONE , a See also:mineral first observed in the 15th See also:century at See also:Tolfa, near See also:Rome, where it is See also:mined for the manufacture of See also:alum. Extensive deposits are also worked in See also:Tuscany and See also:Hungary, and at Bulladelah in New See also:South See also:Wales. By repeatedly roasting and lixiviating the mineral, alum is obtained in See also:solution, and this is crystallized out by evaporation. Alunite occurs as seams in trachytic and allied volcanic rocks, having been formed by the See also:action of sulphureous vapours on these rocks. The See also:white, finely granular masses somewhat resemble See also:limestone in See also:appearance, and the more compact kinds from Hungary are so hard and tough that they are used for millstones. Distinct crystals of alunite are rarely met with in cavities in the massive material; these are rhombohedra with interfacial angles of 9o° 50', so that they resemble cubes in appearance. See also:Minute glistening crystals have also been found loose in cavities in altered See also:rhyolite. The hardness is 4 and the specific gravity 2.6. The mineral is a hydrated basic See also:aluminium and See also:potassium sulphate, KAl3(SO4)2(OH)5. It is insoluble in See also:water, but soluble in sulphuric See also:acid. First called aluminilite by J. C.

Delametherie in 1797, this name was contracted by F. S. See also:

Beudant in 1824 to alunite. (L. J.

End of Article: ALUNITE, or ALUMSTONE

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