mineral

Chalcedony (specifically Agate or Moonstone-like Quartz)

Silicon Dioxide (SiO2)

Hardness: 6.5–7 on the Mohs scale. Color: Translucent milky white with possible opalescence. Luster: Waxy to vitreous. Crystal structure: Cryptocrystalline (hexagonal). Cleavage: None (conchoidal fracture). Specific gravity: 2.6–2.64.

Hardness: 6
Color: Translucent milky white with possible opalescence
Luster: Waxy to vitreous

Identified March 25, 2026More mineral →

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Physical properties

Formation & geological history

Formed through the deposition of silica-rich water in cavities of volcanic rocks (igneous) or sedimentary layers. It typically forms at relatively low temperatures over millions of years.

Uses & applications

Commonly used in jewelry (cabochons and beads), decorative carvings, and as a semi-precious gemstone. Sometimes used in industrial abrasive applications due to its hardness.

Geological facts

Chalcedony has been used for making tools and cylinder seals since at least 2500 BC in Mesopotamia. Many civilizations believed it could ward off evil spirits and bad dreams.

Field identification & locations

Identify in the field by its waxy luster, lack of visible crystals, and conchoidal (glass-like) fracture. Found globally in riverbeds, desert pavements, and volcanic regions like Oregon, India, and Brazil.

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