mineral
Tumbled agate (likely moss or plume agate)
Microcrystalline quartz, primarily chalcedony (SiO₂), with iron-oxide and other mineral inclusions
AI-generated identification · may be incorrectHardness about 6.5–7 Mohs; brown, honey, gray, and cream coloration; waxy to vitreous luster; translucent edges; cryptocrystalline quartz with no obvious cleavage and conchoidal fracture. The rounded, glossy surface indicates tumbling and polishing.
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Physical properties
Hardness about 6.5–7 Mohs; brown, honey, gray, and cream coloration; waxy to vitreous luster; translucent edges; cryptocrystalline quartz with no obvious cleavage and conchoidal fracture. The rounded, glossy surface indicates tumbling and polishing.
Formation & geological history
Agate forms when silica-rich groundwater fills cavities in volcanic rock, depositing chalcedony in layers around inclusions or earlier mineral growths. Individual deposits range from Paleozoic to recent in age and occur worldwide.
Uses & applications
Used for cabochons, beads, carvings, ornaments, and lapidary collections; durable agate is also used for polished decorative objects and historical precision-tool surfaces.
Geological facts
The internal plume or moss-like patterns are mineral inclusions rather than true organic moss. Brown coloration commonly results from iron oxides or hydroxides.
Field identification & locations
Identify agate by its waxy polish, translucency, curved banding or dendritic inclusions, and hardness sufficient to resist scratching by steel. Common sources include Brazil, Uruguay, Mexico, India, Madagascar, and the United States.
