mineral
Green Opal
Opal (Hydrated silica, SiO2·nH2O)
AI-generated identification · may be incorrectHardness: 5.5-6.0 on Mohs scale; Color: Olive to lime green; Luster: Vitreous to waxy/greasy; Structure: Amorphous (non-crystalline); Specific Gravity: 1.9-2.3.
- Hardness
- 5
- Color
- Olive to lime green
- Luster
- Vitreous to waxy/greasy
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Physical properties
Hardness: 5.5-6.0 on Mohs scale; Color: Olive to lime green; Luster: Vitreous to waxy/greasy; Structure: Amorphous (non-crystalline); Specific Gravity: 1.9-2.3.
Formation & geological history
Formed from the deposition of silica-rich waters in the fissures and cavities of igneous rocks, particularly volcanic ash and basalt, often over millions of years.
Uses & applications
Primarily used in jewelry as cabochons, for ornamental carvings, and as a popular specimen for collectors.
Geological facts
Unlike precious opal, green opal does not show 'play of color.' Its hue is often caused by the presence of nickel or chlorite inclusions.
Field identification & locations
Identify by its characteristic waxy luster and conchoidal fracture. Often found in Tanzania, Madagascar, Peru, and Australia. Collectors should look for a uniform pistachio color.
