mineral

Tumbled carnelian (likely agate/chalcedony)

Microcrystalline quartz, SiO₂; reddish color typically from iron oxides

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; translucent orange-red to brown with a waxy or vitreous luster. It has cryptocrystalline quartz structure and no visible cleavage; the rounded shape indicates tumbling or natural abrasion.

Identified August 19, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities in volcanic rocks, later crystallizing as chalcedony and acquiring red coloration through iron oxidation. Individual pieces may range from relatively young weathering deposits to Paleozoic or Mesozoic host rocks.

Uses & applications

Used as an inexpensive gemstone, cabochon, bead, carving material, and lapidary/tumbling stone; also collected for its warm color.

Geological facts

Carnelian is the red-orange variety of chalcedony and grades into banded agate. Stronger color is often enhanced by heating or dyeing, though this specimen appears naturally colored or polished.

Field identification & locations

Commonly found in volcanic terrains and alluvial gravels, especially in Brazil, India, Uruguay, Madagascar, and the western United States. Identify it by its orange-red translucency, quartz-like hardness, waxy luster, and absence of cleavage; a steel file should not easily scratch it.