mineral

Tumbled chalcedony (likely moss or dendritic agate)

Microcrystalline quartz, SiO₂, with iron-oxide inclusions

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; translucent cream to honey-brown, waxy-to-glassy luster, cryptocrystalline structure, and no visible cleavage. Brown patches are likely iron oxides or mineral dendrites; exact identification requires testing.

Identified August 11, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures, later incorporating iron-bearing inclusions; commonly Cenozoic to older volcanic-hosted material. The rounded, polished shape indicates human tumbling.

Uses & applications

Used for cabochons, beads, carvings, and inexpensive jewelry; attractive patterned pieces are popular among collectors. It has little construction or industrial value beyond silica content.

Geological facts

Chalcedony is quartz made of extremely fine intergrowths of quartz varieties. Moss and dendritic patterns are inclusions, not necessarily fossils or organic material.

Field identification & locations

Identify by its waxy translucence, lack of cleavage, and resistance to scratching glass; a steel knife should not scratch it. Common sources include Brazil, India, Uruguay, Madagascar, and the western United States.