mineral

Chalcedony (specifically Blue Chalcedony or Common Opal variety)

Silicon Dioxide (SiO₂)

Hardness: 6.5-7 on Mohs scale; Color: Translucent grayish-blue to milky white; Luster: Waxy to vitreous; Crystal structure: Cryptocrystalline (microscopic quartz); Cleavage: None (conchoidal fracture); Specific gravity: 2.58–2.64.

Hardness: 6
Color: Translucent grayish-blue to milky white
Luster: Waxy to vitreous

Identified March 14, 2026More mineral →

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Physical properties

Formation & geological history

Formed from the deposition of silica-rich hydrothermal fluids in the cavities or fissures of volcanic host rocks (often basalt or rhyolite). This specimen appears to be raw silica material within its rocky matrix.

Uses & applications

Primary uses include lapidary work (cabbing and tumbling), ornamental carvings, and jewelry. It is also a popular specimen for amateur mineral collectors and metaphysical practitioners.

Geological facts

Chalcedony has been used by humans for thousands of years to make tools and weapons because it fractures into sharp edges. The blue variety is often called 'Mohave Blue' or 'African Blue' depending on its locality. It is technically a fibrous form of silica.

Field identification & locations

Identify in the field by its waxy appearance, translucency when held to light, and its ability to scratch glass. It is commonly found in desert regions of the Western USA (Oregon, California), Namibia, and Turkey. Collectors should look for nodules in volcanic beds.

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