mineral

Carnelian agate (likely carnelian geode fragment)

Microcrystalline quartz, SiO₂, chalcedony variety colored by iron oxides

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent orange to reddish-brown interior with white/brown chalcedony rind, waxy to vitreous luster, cryptocrystalline quartz, and no visible cleavage. The glossy surface appears polished or naturally fractured.

Identified September 15, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities in volcanic rock, depositing chalcedony and iron-bearing layers; commonly Cenozoic to older, depending on the host lava. The cavity interior may later weather or be cut open.

Uses & applications

Used for cabochons, beads, carvings, seals, and ornamental specimens; durable enough for jewelry but generally less valuable than fine crystalline quartz gemstones.

Geological facts

Carnelian’s orange-red color results mainly from dispersed hematite or limonite. Agate is banded chalcedony, and this specimen appears to contain massive carnelian rather than strongly developed banding.

Field identification & locations

Identify by its translucent warm color, waxy luster, conchoidal fracture, and hardness sufficient to scratch glass; it should not be confused with orange glass or resin. Common sources include Brazil, Uruguay, India, Madagascar, and the United States.