mineral

Carnelian/chalcedony rough

Microcrystalline quartz (SiO₂), iron-oxide-colored chalcedony

AI-generated identification · may be incorrect

Typically Mohs 6.5–7, orange-red to brown, translucent at edges, with waxy to glassy luster and no visible cleavage; cryptocrystalline quartz has a fibrous aggregate structure. The specimen appears rough and iron-stained, though a definitive identification would require hardness and translucency tests.

Identified August 10, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures, with iron impurities producing red, orange, and brown colors; commonly associated with volcanic rocks and ancient silica deposits. Chalcedony deposits range from Precambrian to recent in age.

Uses & applications

Used as a gemstone, cabochon, bead, carving material, and ornamental stone; rough pieces are popular with collectors. Common material is modestly priced.

Geological facts

Carnelian is the reddish variety of chalcedony, while darker brown material may be called sard. Color can intensify through natural weathering or heat treatment.

Field identification & locations

Common localities include India, Brazil, Uruguay, Madagascar, Namibia, and the United States. Look for waxy luster, curved fracture, translucency, and resistance to scratching glass; avoid confusing it with dyed glass or jasper.