mineral

Blue Chalcedony

Cryptocrystalline Silicon Dioxide (SiO2)

Hardness: 6.5-7 (Mohs scale); Color: Pale blue to lavender; Luster: Waxy to vitreous; Crystal Structure: Trigonal (cryptocrystalline); Cleavage: None; Specific Gravity: 2.58-2.64

Hardness: 6
Color: Pale blue to lavender
Luster: Waxy to vitreous

Identified June 3, 2026More mineral →

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Physical properties

Hardness: 6.5-7 (Mohs scale); Color: Pale blue to lavender; Luster: Waxy to vitreous; Crystal Structure: Trigonal (cryptocrystalline); Cleavage: None; Specific Gravity: 2.58-2.64

Formation & geological history

Formed via the deposition of silica from low-temperature hydrothermal solutions in cavities of volcanic rocks or sedimentary environments. It can occur in nearly any geological age where secondary silica mineralization is present.

Uses & applications

Used extensively in jewelry for cabochons and beads, as well as for ornamental carvings, polished points, and lapidary art.

Geological facts

Blue chalcedony is often translucent with a ghostly inner glow caused by the Tyndall effect, where light is scattered by fine microscopic particles. Ancient Greeks and Romans used it for cylinder seals and signet rings.

Field identification & locations

Identify in the field by its waxy luster, conchoidal fracture, and lack of visible crystals. It is commonly found in Turkey, Namibia, India, and the United States (Oregon and California).

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