mineral

Dendritic Agate (Tree Agate)

Chalcedony (Silicon Dioxide, SiO2) with Manganese or Iron Oxide inclusions

Hardness: 6.5-7 (Mohs scale); Color: White, gray, or translucent base with dark branch-like patterns; Luster: Waxy to vitreous; Crystal Structure: Trigonal/Microcrystalline; Cleavage: None; Specific Gravity: 2.58-2.64

Hardness: 6
Luster: Waxy to vitreous

Identified February 19, 2026More mineral →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Formed when mineral-rich water (containing manganese or iron) seeps into cracks in chalcedony or limestone. The patterns grow in a fractal manner similar to frost. Most specimens are found in volcanic rocks or alluvial deposits and can be millions of years old.

Uses & applications

Primarily used in jewelry (cabochons), lapidary art, and as a collector's specimen. In industry, high-quality chalcedony can be used as a precision bearing or abrasive.

Geological facts

The term 'dendrite' comes from the Greek word 'dendron' meaning tree. Despite the botanical appearance, these patterns are purely mineral and contain no organic fossil material. They are often mistaken for fossilized moss or ferns.

Field identification & locations

Identify in the field by its characteristic 'fern-like' or 'branch-like' black or brown patterns against a lighter rock matrix. It is commonly found in India, Brazil, and the Western United States. Collectors should look for high contrast and clear patterns.

Other mineral specimens

See all

Sandstone (with potential mineral staining/concretions)

Arenite (SiO2 based)

sedimentary

Epidote

Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)

metamorphic

Nephrite Jade

Nephrite

Mineral/Rock

Banded Gneiss (River Rock/Pebble)

Gneiss (specifically a banded variety often found as a river rock)

Metamorphic Rock

Green Apatite on Albite

Fluorapatite [Ca5(PO4)3F] on Albite [Na(AlSi3O8)]

mineral

Epidote

Epidote - Ca2(Al2,Fe3+)3(SiO4)3(OH)

mineral