mineral

Carnelian Agate

Silicon Dioxide (SiO2) - variety of Chalcedony

Hardness: 6.5-7 (Mohs), Color: Orange-red to brownish-red, Luster: Waxy to vitreous, Crystal Structure: Trigonal (microcrystalline/cryptocrystalline), Cleavage: None/Conchoidal fracture, Specific Gravity: 2.58-2.64

Hardness: 6

Identified June 2, 2026More mineral →

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Physical properties

Formation & geological history

Formed through the deposition of silica in gas cavities of volcanic rocks. The red-orange hue comes from iron oxide (hematite) impurities dispersed within the silica structure.

Uses & applications

Used primarily in lapidary arts, jewelry making (cabochons, beads), decorative carvings, and as a popular collector's tumbled stone.

Geological facts

Carnelian was used widely in the ancient world for cylinder seals and signet rings because hot wax does not stick to it. It has been mined since the Neolithic period.

Field identification & locations

Identify in the field by its translucency and waxy luster compared to jasper; look for it in volcanic riverbeds or coastal gravels in places like Brazil, India, or the Pacific Northwest, USA.

Other mineral specimens

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Sandstone (with potential mineral staining/concretions)

Arenite (SiO2 based)

sedimentary

Schist

Metamorphic

Epidote

Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)

metamorphic

Nephrite Jade

Nephrite

Mineral/Rock

Banded Gneiss (River Rock/Pebble)

Gneiss (specifically a banded variety often found as a river rock)

Metamorphic Rock

Biotite Schist

Biotite-rich Schist [K(Mg,Fe)3AlSi3O10(F,OH)2]

metamorphic