mineral

Chalcedony (Grey/White Agate)

Silicon Dioxide (SiO₂)

AI-generated identification · may be incorrect

Hardness: 6.5–7 on the Mohs scale. Color: Translucent greyish-white. Luster: Waxy to vitreous. Crystal Structure: Trigonal/Monoclinic (Cryptocrystalline). Cleavage: None (Conchoidal fracture). Specific Gravity: 2.58–2.64.

Hardness: 6
Color: Translucent greyish-white
Luster: Waxy to vitreous

Identified March 25, 2026More mineral →

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Physical properties

Formation & geological history

Formed through the deposition of silica from groundwater in cavities of volcanic rocks (igneous) or sedimentary layers. This process occurs at relatively low temperatures over millions of years.

Uses & applications

Used primarily in lapidary work for cabochons, beads, and jewelry. Also used for ornamental carvings, mortar and pestles due to its hardness, and as a semi-precious collector's specimen.

Geological facts

Chalcedony is a cryptocrystalline form of silica, meaning its crystals are too small to be seen under a standard microscope. It was highly valued in antiquity for seal stones because hot wax does not stick to it.

Field identification & locations

Identify in the field by its waxy appearance, translucency when held to light, and ability to scratch glass. Commonly found in riverbeds or gravel deposits near volcanic regions. Tips for collectors: look for 'conchoidal' fractures that resemble chipped glass.