ALUNITE or ALUMSTONE, a mineral first observed in the century at Tolfa, near Rome, where it is mined for the manu facture of alum. Extensive deposits are also worked in Tuscany and Hungary, and at Bulladelah in New South Wales. By repeat edly roasting and lixiviating the mineral, alum is obtained in solu tion, and this is crystallized out by evaporation. Alunite occurs as seams in trachytic and allied volcanic rocks, having been f ormed by the action of sulphurous vapours on these rocks. The white, finely granular masses somewhat resemble marble in appearance, and the more compact kinds from Hungary are so hard and tough that they are used for millstones. The hardness is 4 and the spe cific gravity 2.6. The mineral is a hydrated basic aluminium and potassium sulphate,