either of two gem minerals, one a plagioclase feldspar and the other quartz. Both have a sparkling reflection from oriented minute inclusions of mica or hematite.

Most aventurine quartz is silvery, yellow, reddish brown, or green. Extensive beds in mica schist occur in the Russian Urals. Green aventurine, coloured by a chrome mica, has been found in the state of Tamil Nadu (formerly Madras), India; in China; and in Rutland, Vt. Aventurine quartz is used for jewelry, for vases and bowls (sometimes very large), and for other ornamental objects.