mineral

Chalcedony

Silicon Dioxide (SiO2)

Hardness: 6.5-7 on Mohs scale. Color: Pale blue, grey, or white. Luster: Waxy to vitreous. Crystal structure: Cryptocrystalline (hexagonal). Cleavage: None. Specific Gravity: 2.6-2.64.

Hardness: 6
Color: Pale blue, grey, or white
Luster: Waxy to vitreous

Identified July 19, 2026More mineral →

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Physical properties

Hardness: 6.5-7 on Mohs scale. Color: Pale blue, grey, or white. Luster: Waxy to vitreous. Crystal structure: Cryptocrystalline (hexagonal). Cleavage: None. Specific Gravity: 2.6-2.64.

Formation & geological history

Formed from the deposition of silica-rich fluids in volcanic cavities, sedimentary rocks, or along hydrothermal veins. It often forms at low temperatures.

Uses & applications

Used primarily in lapidary work for cabochons, beads, and carvings. Also used historically for seals and tools due to its toughness.

Geological facts

Chalcedony is a broad term for cryptocrystalline quartz. Varieties include agate, jasper, and carnelian. It was named after the ancient Greek town of Chalkedon.

Field identification & locations

Identify by its waxy luster, lack of visible crystals, and conchoidal fracture. Often found as nodules or lining geodes. Common in basaltic areas and river beds.