mineral

Blue Chalcedony

Chalcedony (Silicon Dioxide, SiO2)

Hardness: 6.5–7 on Mohs scale. Color: Pale blue to lavender-blue with a waxy luster. Crystal structure: Cryptocrystalline (microscopic quartz fibers). Cleavage: None. Specific gravity: 2.58–2.64. Diaphaneity: Translucent.

Hardness: 6
Color: Pale blue to lavender-blue with a waxy luster

Identified February 14, 2026More mineral →

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Physical properties

Formation & geological history

Formed from the deposition of silica-rich groundwater in cavities of igneous rocks or sedimentary environments. It is often found in volcanic pockets known as geodes or as masses in sedimentary layers. Formation can date from various geological periods depending on host rock location.

Uses & applications

Used extensively in jewelry as cabochons, beads, and carvings. Also used in ornamental decorative objects, seals, and historically for cameos and intaglios due to its toughness and uniform texture.

Geological facts

Chalcedony was highly prized in the ancient world; many ancient civilizations, including the Romans and Greeks, used it for signet rings. The name likely derives from the ancient Greek town of Chalkedon in Asia Minor.

Field identification & locations

Identify by its waxy luster, lack of visible crystals, and its ability to scratch glass. Usually found in Turkey, Namibia, India, and the United States (Oregon/California). Collectors look for uniform color and high translucency without dark inclusions.

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