mineral

Dendritic Agate

Silicon Dioxide (SiO2) with Manganese/Iron oxide inclusions

Hardness: 6.5–7 (Mohs scale); Color: Translucent white or gray with dark branching inclusions; Luster: Waxy to vitreous; Crystal Structure: Hexagonal (cryptocrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.58–2.64.

Hardness: 6
Color: Translucent white or gray with dark branching inclusions
Luster: Waxy to vitreous

Identified April 5, 2026More mineral →

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Physical properties

Formation & geological history

Formed when mineral-rich groundwater (containing manganese or iron) seeps into cracks in quartz-based rocks or volcanic cavities, leaving behind tree-like 'dendritic' patterns as it crystallizes over thousands of years.

Uses & applications

Primarily used in jewelry (cabochons), ornamental carvings, and as a popular specimen for rock collectors and lapidary enthusiasts.

Geological facts

Despite its name, it is technically a chalcedony rather than a true agate because it lacks the classic concentric banding. The patterns are strictly mineral deposits and not fossilized plants.

Field identification & locations

Identify in the field by its translucency and characteristic 'fern-like' or 'moss-like' inclusions. Common in Brazil, India, Madagascar, and the USA (notably Montana). Look for smooth, waxy surfaces on weathered nodules.

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