mineral
Dendritic Agate
Silicon Dioxide (SiO2) with Manganese/Iron inclusions
Hardness: 6.5-7 Mohs; Color: White to grey base with black or brown tree-like inclusions; Luster: Waxy to vitreous; Crystal structure: Trigonal (microcrystalline); Cleavage: None
- Hardness
- 6
- Color
- White to grey base with black or brown tree-like inclusions
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5-7 Mohs; Color: White to grey base with black or brown tree-like inclusions; Luster: Waxy to vitreous; Crystal structure: Trigonal (microcrystalline); Cleavage: None
Formation & geological history
Formed when mineral-rich water, usually containing manganese or iron oxides, seeps into cracks in chalcedony or volcanic rock, depositing minerals in branching patterns over millions of years.
Uses & applications
Commonly used in jewelry (cabochons), ornamental carvings, and as a popular collector's specimen due to its unique patterns.
Geological facts
Despite being called 'Dendritic Agate,' it is technically a chalcedony because it lacks the concentric banding required to be a true agate. The patterns are often called 'pseudofossils' because they look like plants but are purely mineral.
Field identification & locations
Identify by its translucent milky base and fractal, branch-like inclusions. Common in Brazil, India, and the United States (specifically Montana). Collectors look for high contrast between the background and the 'branches'.
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