Green Aventurine

India is by far the most important commercial producer of aventurine and Brazil is second; smaller amounts come from Russia, Spain, Austria and Tanzania. Aventurine is a variety of quartzite, a metamorphic rock formed when quartz sandstone or chert recrystallizes into a tight network of quartz grains. Gemdat lists Metri in the Ballari District of Karnataka, India, and Mariazell in Styria, Austria, among significant localities.

Magnification with darkfield lighting shows the tiny green mica platelets that cause the colour. Under a Chelsea filter green aventurine appears reddish, and a spectroscope may show broad bands near 648 and 682 nm. Its refractive index (about 1.54 to 1.55) and specific gravity (about 2.66) are well below those of jadeite (1.66 to 1.69; about 3.34). Many green beads are oiled to darken them or dyed, and much material sold as "aventurine" shows little or no aventurescence; dye concentrations can be seen with magnification. Goldstone (aventurine glass) is distinguished by its much lower hardness and by its uniform copper crystals, whose shape can readily be made out with a lens.

Aventurine has the hardness of quartz (6.5 to 7), but abundant mica can lower its apparent hardness and give it a direction of easier breakage, and coarse mica flakes can pluck out of a polished surface and leave pits. IGS lists no special care for quartz, but notes that some dyes used on quartz fade, which matters for the oiled or dyed beads that are common in the trade.

Mindat derives the name from the Italian "a ventura", meaning "by chance", and links it to aventurine glass, a glittering glass with copper inclusions first made in Italy. Mindat also notes that "aventurine" is used commercially for several kinds of stones, including aventurine feldspar (sunstone); the natural quartz material is also called aventurine quartz and is not to be confused with aventurine glass (goldstone). Because of its colour and low price, green aventurine has been used as an alternative to jade and amazonite, and IGS lists "Indian jade" as a misnomer for green aventurine quartz.

The Japanese retailer Pascle writes that green aventurine is said to ease bodily tiredness and help relaxation, and presents it as a stone of healing.

In modern crystal-healing practice green aventurine is commonly used to represent the fourth, or heart, chakra. Geology.com notes that such practices have not been scientifically proven and that medical experts consider reported benefits to be a placebo effect.