sedimentary
Mocha Stone (Dendritic Agate)
Silicon Dioxide (SiO2) with Manganese/Iron inclusions
Hardness: 6.5-7 Mohs; Color: Translucent grey to tan with tree-like inclusions; Luster: Vitreous to waxy; Structure: Cryptocrystalline quartz; Cleavage: None.
- Hardness
- 6
- Color
- Translucent grey to tan with tree-like inclusions
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 6.5-7 Mohs; Color: Translucent grey to tan with tree-like inclusions; Luster: Vitreous to waxy; Structure: Cryptocrystalline quartz; Cleavage: None.
Formation & geological history
Formed as silica-rich groundwater fills cavities in volcanic or sedimentary rocks, with trace minerals like manganese forming dendritic (tree-like) patterns as they crystalize.
Uses & applications
Used primarily in lapidary work, jewelry making (cabochons), and as a collector's pocket stone or decorative tumbled stone.
Geological facts
Also known as 'Mocha Stone,' it was historically highly prized in India. The name 'dendritic' comes from the Greek word 'dendron,' meaning tree, referring to its plant-like patterns.
Field identification & locations
Identified by its translucent body and dark, branching patterns. Commonly found in Brazil, India, Madagascar, and the USA (Montana/Oregon). Look for 'organic' looking mineral growths inside clear/grey stone.
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