mineral

Chalcedony (Agate/Carnelian variant)

Silicon Dioxide (SiO2)

Hardness: 6.5-7 Mohs; Color: Translucent grey, white, and orange; Luster: Waxy to vitreous; Crystal Structure: Trigonal (cryptocrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.58-2.64.

Hardness: 6
Color: Translucent grey, white, and orange
Luster: Waxy to vitreous

Identified July 12, 2026More mineral →

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Physical properties

Formation & geological history

Formed from the deposition of silica from groundwater in cavities of volcanic and sedimentary rocks. This specimen shows typical cryptocrystalline structure associated with low-temperature hydrothermal environments.

Uses & applications

Used primarily in lapidary arts for jewelry, carvings, and tumbled stones. Historically used for making tools due to its conchoidal fracture and hardness.

Geological facts

Chalcedony is a cryptocrystalline form of silica, meaning its crystals are too small to be seen even under a microscope. It has been used for seals and jewelry for thousands of years, dating back to the Bronze Age in the Mediterranean.

Field identification & locations

Identify in the field by its waxy luster, translucency, and lack of visible grains. It often occurs as nodules or fillings in rock cavities. Found globally, particularly in volcanic regions like the Pacific Northwest, Brazil, and India.

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