sedimentary
Dendritic Jasper (River Stone)
Silicon Dioxide (SiO2) with Manganese/Iron Oxide inclusions
Hardness: 6.5-7 (Mohs scale); Color: Yellow-brown with black/dark brown dendritic patterns; Luster: Vitreous to waxy; Structure: Microcrystalline; Cleavage: None (conchoidal fracture).
- Hardness
- 6
- Color
- Yellow-brown with black/dark brown dendritic patterns
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 6.5-7 (Mohs scale); Color: Yellow-brown with black/dark brown dendritic patterns; Luster: Vitreous to waxy; Structure: Microcrystalline; Cleavage: None (conchoidal fracture).
Formation & geological history
Formed from the deposition of silica-rich fluids in volcanic ash or sedimentary beds. The 'tree-like' patterns (dendrites) are created when mineral-rich water (manganese or iron) seeps into cracks in the jasper and crystallizes. This specimen shows significant river-worn rounding, indicating long-term transport in water.
Uses & applications
Used primarily for lapidary work, jewelry (cabochons), interior decoration (polished stones), and as healing stones in metaphysical practices.
Geological facts
The term 'dendritic' comes from the Greek word 'dendron,' meaning tree. These patterns are often mistaken for fossilized plants or mosses, but they are purely inorganic mineral growths similar to frost on a window.
Field identification & locations
Identify by its hardness (will scratch glass), smooth water-worn texture, and distinct branching black patterns against an opaque yellow background. Common in riverbeds in the Western US, Brazil, and India.
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