mineral

Tumbled dendritic agate (likely moss agate)

Microcrystalline quartz, SiO₂, with iron/manganese oxide inclusions

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; gray, cream, black, and rusty-brown patterns; vitreous to waxy luster; cryptocrystalline quartz with no visible cleavage and conchoidal fracture. The rounded, polished surface indicates tumbling.

Identified August 22, 2026More mineral →

Explore Tumbled dendritic agate (likely moss agate) in the encyclopedia →

Identify your own rocks.

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

App Store Google Play

Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities in volcanic rock, depositing chalcedony and later iron/manganese oxides that create dendritic or moss-like inclusions. Most specimens are Cenozoic to older, depending on locality.

Uses & applications

Used for cabochons, beads, carvings, ornaments, and lapidary collections; generally valued for pattern and polish rather than rarity.

Geological facts

Dendritic markings are mineral-growth patterns, not fossils or plant material. Agate commonly develops concentric or irregular bands as silica composition changes during cavity filling.

Field identification & locations

Commonly found in volcanic terrains, especially Brazil, India, Uruguay, Madagascar, Mexico, and the western United States. Identify by its waxy translucent edges, very high scratch resistance, and natural-looking internal inclusions; glass may resemble it but is often more uniformly clear.