AVENTURINE, or AVANTURINE  , a variety of quartz containing spangles of mica or scales of iron-oxide, which confer brilliancy on the stone . It is found chiefly in the Ural Mountains, and is cut for ornamental purposes at Ekaterinburg . Some of the Siberian aventurine, like that of the vase given by Nicholas I. to Sir R . Murchison, in 1843, is a micaceous iron-stained quartz, of but little beauty . Most aventurine is of reddish brown or yellow colour, but a green variety, containing scales of fuchsite or chrome-mica, is also known . This green aventurine, highly valued by the Chinese, is said to occur in the Bellary district in India . Aventurine felspar, known also as Sun-stone (q.v.) is found principally at Tvedestrand in south Norway, and is a variety of oligoclase enclosing micaceous scales of haematite . Other kinds of felspar, even orthoclase, may however also show the aventurine appearance . Both plagioclastic and orthoclastic aventurine occur at several localities in the United States . The mineral aventurine takes its name from the well-known aventurine-glass of Venice . This is a reddish brown glass with gold-like spangles, more brilliant than most of the natural stone . The story runs that this kind of glass was originally made accidentally at Murano by a workman, who let some copper filings fall into the molten " metal," whence the product was called avventurino .

From the Murano glass the name passed to the mineral, which displayed a rather similar appearance . (F . W .