mineral
Dendritic Opal
Dendritic Common Opal (SiO2·nH2O with Manganese oxide inclusions)
AI-generated identification · may be incorrectHardness: 5.5-6.5; Color: Milky white to cream with black/brown branching patterns; Luster: Vitreous to waxy; Crystal structure: Amorphous; Cleavage: None (conchoidal fracture); Specific gravity: 2.15
- Hardness
- 5
- Color
- Milky white to cream with black/brown branching patterns
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 5.5-6.5; Color: Milky white to cream with black/brown branching patterns; Luster: Vitreous to waxy; Crystal structure: Amorphous; Cleavage: None (conchoidal fracture); Specific gravity: 2.15
Formation & geological history
Formed as silica-rich groundwater seeps into cracks in host rocks. The 'dendrite' tree-like patterns are formed by the precipitation of manganese or iron oxides during the opal's formation.
Uses & applications
Primarily used in jewelry making for cabochons, wire wrapping, and as decorative pocket stones or meditation tools in 'crystal healing' circles.
Geological facts
Despite their appearance, the dark patterns are not fossilized plants or moss; they are geological crystal growths known as dendrites, named after the Greek word for 'tree'.
Field identification & locations
Identify in the field by its characteristic 'fern-like' or 'branching' dark inclusions against an opaque white or translucent background. It lacks the 'play-of-color' fire found in precious opal.
