mineral
Tumbled amber-brown chalcedony (probable carnelian/ag ate)
Microcrystalline quartz, SiO₂; likely iron-stained chalcedony (carnelian)
AI-generated identification · may be incorrectTranslucent honey-brown to gray, waxy luster, curved surfaces, and no visible cleavage; quartz hardness is about 7 Mohs and specific gravity about 2.6. The rounded shape appears tumbled or naturally waterworn, and the gray piece may be related chalcedony.
Identified More mineral →
Explore Tumbled amber-brown chalcedony (probable carnelian/ag ate) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Translucent honey-brown to gray, waxy luster, curved surfaces, and no visible cleavage; quartz hardness is about 7 Mohs and specific gravity about 2.6. The rounded shape appears tumbled or naturally waterworn, and the gray piece may be related chalcedony.
Formation & geological history
Chalcedony forms when silica-rich groundwater fills cavities and fractures, later becoming microcrystalline quartz; iron oxides create orange-brown coloration. Its precise geological age and locality cannot be determined from the photograph.
Uses & applications
Used for beads, cabochons, carvings, ornamental objects, and lapidary collections; chalcedony is also used decoratively in architecture. Common material generally has modest value unless color, translucency, pattern, or provenance is exceptional.
Geological facts
Carnelian is the orange-red variety of chalcedony, while paler brown material is often marketed as sard or brown chalcedony. Heat treatment can intensify its red-orange color.
Field identification & locations
Commonly found in volcanic cavities, silica-rich veins, and alluvial gravels worldwide, especially Brazil, India, Madagascar, Uruguay, and the United States. Field tests include hardness sufficient to scratch glass and lack of reaction to dilute acid; confirm with a gemological test because appearance alone is inconclusive.
