mineral

Dendritic Agate (River Pebble)

Silicon Dioxide (SiO2) with Manganese or Iron oxide inclusions

AI-generated identification · may be incorrect

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 →

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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.