The third form of quartz the Sarah briefly touched on is the microcrystalline form that contains very small but not microscopic quartz crystals. Varieties such as quartzite, tiger’s eye and aventurine are microcrystalline aggregates of many small crystals. The image to the left shows a tiger’s eye and an aventurine stone.
Tiger’s eye is a quartz variety is know for its yellow and brown bands that shift in color with the stone is turned. Tiger’s eye is often heat-treated to produce its reddish brown hue. This interesting stone is commonly cut into cabochons and beads.
Small green mica inclusions create the glittery aventurescence in the aventurine quartz stone above. Like tiger’s eye, aventurine quartz is often cut into cabochons and beads.
Author: Michelle M. Rahm is a GIA-trained Graduate Gemologist and is President of Colorado’s Mile High Chapter of the GIA Alumni Association. She has been selling gemstones and jewelry online since 1997. Visit her websites JewelryImpressions.com and OurCustomWeddingRings.com