Aventurine is a translucent green to bluish-green tectosilicate rock that is a variety of quartz. Aventurine's 'aventurescence' or glistening, shimmering effect is the result of uniformly oriented, platy mineral inclusions within the rock matrix. The presence of fuchsite inclusions, a chrome-bearing variety of muscovite mica, gives aventurine its characteristic silvery greenish-blue sheen. High quantities of fuchsite can cause aventurine to be totally opaque. The name "Aventurine" is derived from the Italian name "a ventura" or "by chance."
Aventurine is typically cut into a cabochon or beads. The principal sources for green Aventurine is in the Madras, Mysore, Nadu, or Tamil regions of India. Secondary sources are in the Ural Mountains of Russia, Minas Gerais, Brazil, and Vermont, USA.
Aventurine Necklace by Natalie Baroni
Certain varieties of Aventurine can have a brown (pyrite), orange (hematite), or yellowish-orange hue. Sunstone can be confused with orange and red aventurine quartzite (above, right), although sunstone can be more transparent. Aventurine can be noticeably banded, and opaque varieties can be mistaken for malachite.
Aventurine has a hardness of 6 1/2 to 7 on the Mohs scale. The Toughness of Aventurine is Fair to Good. Aventurine belongs to the Hexagonal or Trigonal trapezohedral crystal system with a aggregate Massive crystal habit. Specific gravity is between 2.64 and 2.69. Aventurine has a refractive index of 1.550, and a vitreous to dull luster.
Chemical composition: K(Al,Cr)2AlSi3O10(OH)2
Semi-Precious Stones