mineral

Chalcedony

Silicon Dioxide (SiO2)

Hardness: 6.5-7 on Mohs scale. Color: Translucent white, grey, or tan with a waxy luster. Crystal structure: Cryptocrystalline (microscopic crystals). Fracture: Conchoidal. Cleavage: None.

Hardness: 6
Color: Translucent white, grey, or tan with a waxy luster

Identified July 9, 2026More mineral →

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Physical properties

Hardness: 6.5-7 on Mohs scale. Color: Translucent white, grey, or tan with a waxy luster. Crystal structure: Cryptocrystalline (microscopic crystals). Fracture: Conchoidal. Cleavage: None.

Formation & geological history

Formed from the deposition of silica-rich groundwater in cavities of various rock types, especially volcanic rocks and sedimentary limestones, over thousands to millions of years.

Uses & applications

Used primarily in jewelry (cabochons and beads), as an ornamental stone, and historically for making sharp tools like arrowheads due to its conchoidal fracture.

Geological facts

In many cultures, chalcedony is considered a stone of brotherhood and goodwill. It is a broad term that encompasses many varieties including agate, carnelian, and onyx.

Field identification & locations

Identify in the field by its waxy luster, translucency when held to light, and lack of visible grains. Common in riverbeds and volcanic regions worldwide.