mineral

Dendritic Agate (River Pebble)

Silicon Dioxide (SiO2) with Manganese or Iron oxide inclusions

Hardness: 6.5-7 (Mohs); Color: Translucent white to yellow with black/brown branching patterns; Luster: Vitreous to waxy; Structure: Microcrystalline; Specific Gravity: 2.58-2.64

Hardness: 6
Luster: Vitreous to waxy

Identified March 24, 2026More mineral →

Identify your own rocks.

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

App Store Google Play

Physical properties

Hardness: 6.5-7 (Mohs); Color: Translucent white to yellow with black/brown branching patterns; Luster: Vitreous to waxy; Structure: Microcrystalline; Specific Gravity: 2.58-2.64

Formation & geological history

Formed through the cooling of silica-rich groundwater in cavities of volcanic rock or sedimentary layers. The 'tree-like' dendrites form when manganese-rich water seeps into cracks during the stone's formation over millions of years.

Uses & applications

Commonly used in lapidary work for cabochons, jewelry (pendants and rings), and as a decorative 'worry stone' or collector's specimen.

Geological facts

Despite the name, Agate is technically a variety of Chalcedony. The 'dendrites' are often mistaken for fossilized plants or moss, but they are actually inorganic metallic crystal growths, much like frost on a window.

Field identification & locations

Identify by its translucency and characteristic 'fern-like' or 'mossy' internal patterns. These are frequently found as water-worn pebbles in riverbeds and on beaches in volcanic regions.

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