1911 Encyclopædia Britannica/Aventurine

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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 The story runs that this kind of glass was originally made accidentally at Murano by a workman, who let some copper filings fall into the molten metal, whence the product was called avventurino.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. R.*)