Dendritic Agate

Physical Properties

Hardness: 6.5-7 (Mohs scale); Color: Translucent white or gray with dark, tree-like branching inclusions; Luster: Waxy to vitreous; Crystal system: Hexagonal (cryptocrystalline); Specific gravity: 2.60-2.65.

Formation & Geological History

Formed when mineral-rich water (carrying manganese or iron) seeps into cracks in chalcedony or volcanic rock, depositing minerals in branching fern-like patterns known as dendrites. These can form in various geological ages inside volcanic host rocks.

Uses & Applications

Primarily used as a gemstone for jewelry (cabochons), lapidary art, and as a popular collector's specimen due to its unique patterns.

Geological Facts

Although called an agate, it is technically an agate-like chalcedony because it lacks the traditional concentric banding of true agates. The name 'dendrite' comes from the Greek word 'dendron', meaning tree.

Field Identification & Locations

Identify in the field by its distinctive 'plant-like' patterns that are actually mineral growths, its hardness (it will scratch glass), and its translucent matrix. Common locations include Brazil, India, Madagascar, and the USA (Montana/Kansas).

Identified on: 4/25/2026

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