Black Obsidian Glass Specimen, Oregon.
Black Obsidian Glass Specimen, Oregon.

Obsidian is a naturally occurring glass of volcanic origin, having an amorphous structure due to rapid cooling. It can be gray to black and often displays splotchy white patches or “snowflakes”. Obsidian can also be brown to orange or red and have bands or a sheen. Iridescent obsidian is known as rainbow obsidian. Small translucent rounded pieces are called Apache tears. Obsidian gets its name from a Obsius who is said to have discovered it in Ethiopia. Obsidian has been known and used since antiquity.

Gemological Information for Obsidian

Color:Gray, Black, Brown, Orange or Red
Crystal Structure:Amorphous
Refractive Index:1.49 (+0.20 to -.010)
Hardness:5 to 5.5
Similar Stones:Chalcedony and Manmade Glass
Country of Origin:Worldwide

Obsidian Care

Ultrasonic Cleaning:Safe
Steam Cleaning:Not Safe
Warm Soapy Water:Safe
Chemical Attack:Hydrofluoric Acid Will Attack
Light Sensitivity:Stable
Heat Sensitivity:May Crack or Brake with Rapid Changes in Temperature


  • Gem Reference Guide, Los Angeles: Gemological Institute of America, 1988. Pp. 132-134.
  • Newman, Harold. An Illustrated Dictionary of Jewelry, New York: Thames and Hudson, 1981. Pp. 219.
  • Schumann, Walter. Gemstones of the World, New York: Sterling Publishing, Co., 1977. Pp. 212.
Close Menu