Obsidian
Mahogany Obsidian
Indonesia
69.01 carats
© gemselect.com
Obsidian is a naturally occurring volcanic glass. It is usually an opaque black or grey but may be yellow, red, greenish brown. Obsidian may have an iridescent sheen caused by inclusions.
Obsidian is used for ornamental purposes and as a gemstone.
Many colored glasses are sold as "obsidian" often claiming to be natural.
Obsidian Gemstones by Colour
This table shows the variety of hues this gemstone can be found in. Click on a photo for more information.
|  |  |
 |
 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Obsidian Gemstones by Size
This table shows distribution of Obsidian gemstone sizes that are listed on this site. This can give a good indication as to the general availability of this gemstone in different sizes.
Contributed photos
Lightest:0.16 cts
Heaviest:168.6 cts
Average:34.77 cts
Total photos:33
Do you have a larger Obsidian? Why not upload a photo?
| General Information | ||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| A variety or type of: | Glass | |||||||||||||||
| Varieties/Types: | Apache Tears - Small rounded pebbles of black Obsidian found in American Southwest. Mahogany Obsidian - A variety of Obsidian with black and red banding. Rainbow Obsidian - Obsidian with multicolored iridescence. Sheen Obsidian - A variety of obsidian exhibiting a golden sheen effect. Snowflake Obsidian - A variety of obsidian containing white "snowflake" crystal patterns of the mineral cristobalite. | |||||||||||||||
| Obsidian Simulants | ||||||||||||||||
| Many. colored glasses are sold as "obsidian" especially, often flawless and brightly colored. These are obvious inexpensive fakes. | ||||||||||||||||
| Physical Properties of Obsidian | ||||||||||||||||
| Mohs Hardness | 5 to 5.5, Blue Chart Gem Identification (2010) More from other references | |||||||||||||||
| Specific Gravity | 2.35 to 2.60, Gemstones of the world (2001) More from other references | |||||||||||||||
| Cleavage Quality | None, Gemstones of the world (2001) | |||||||||||||||
| Fracture | Conchoidal, Gemstones of the world (2001) Large conchoidal, sharp edgedMore from other references | |||||||||||||||
| Optical Properties of Obsidian | ||||||||||||||||
| Refractive Index | 1.450 to 1.550, Blue Chart Gem Identification (2010) More from other references | |||||||||||||||
| Optical Character | Isotropic, Gemstones (2009) | |||||||||||||||
| Birefringence | None, Gemstones of the world (2001) | |||||||||||||||
| Pleochroism | Absent, Gemstones of the world (2001) | |||||||||||||||
| Dispersion | 0.010, Gemstones of the world (2001) | |||||||||||||||
| Colour | ||||||||||||||||
| Colour (General) | Black, brown, partly iridescent or with silvery or golden sheen (opaque) Brown, green, red (transparent), Gemmological Tables (2004) More from other references | |||||||||||||||
| Transparency | Transparent,Translucent,Opaque, Gemmological Tables (2004) More from other references | |||||||||||||||
| Lustre | Vitreous, Gemstones (2009) | |||||||||||||||
| Fluorescence & other light emissions | ||||||||||||||||
| Fluorescence (General) | None, Gemstones of the world (2001) | |||||||||||||||
| Crystallography of Obsidian | ||||||||||||||||
| Crystal System | Amorphous, Blue Chart Gem Identification (2010) More from other references | |||||||||||||||
| Habit | Massive, Gemstones (2009) | |||||||||||||||
| Geological Environment | ||||||||||||||||
| Where found: | Occurs when volcanic lava is subjected to rapid heat loss., Gemstones (2009) | |||||||||||||||
| Inclusions in Obsidian | ||||||||||||||||
| Torpedo shaped gas bubbles, needle-like inclusions, smooth undulating growth structure - Blue Chart Gem Identification, Herve Nicolas Lazzarelli, 2010, p 8 Gas bubbles, swirl marks, crystal inclusions, white spherolites ("snow flake obsidian") - Gemmological Tables, Ulrich Henn and Claudio C. Milisenda, 2004, p 2 | ||||||||||||||||
| Further Information | ||||||||||||||||
| Mineral information: | Obsidian information at mindat.org | |||||||||||||||
| Significant Gem Localities | ||||||||||||||||
| ||||||||||||||||