mineral

Blue Chalcedony

Cryptocrystalline Quartz (SiO2)

Hardness: 6.5-7 on Mohs scale; Color: pale blue, lavender, or grey-blue; Luster: waxy to vitreous; Crystal structure: Trigonal (microcrystalline); Cleavage: none; Specific gravity: 2.58-2.64.

Hardness: 6
Color: pale blue, lavender, or grey-blue
Luster: waxy to vitreous

Identified June 14, 2026More mineral →

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Physical properties

Hardness: 6.5-7 on Mohs scale; Color: pale blue, lavender, or grey-blue; Luster: waxy to vitreous; Crystal structure: Trigonal (microcrystalline); Cleavage: none; Specific gravity: 2.58-2.64.

Formation & geological history

Formed at relatively low temperatures in the cavities of volcanic and sedimentary rocks. It precipitates from silica-rich groundwater. Age varies by location but is commonly found in Cenozoic formations.

Uses & applications

Primarily used as a gemstone for jewelry (cabochons, beads), decorative carvings, and as a collector's specimen. Known historically as a medium for cylinder seals in Mesopotamia.

Geological facts

Blue chalcedony was used in ancient Rome for signet rings and cameos. It is often referred to as 'Mohave Blue' or 'African Blue' depending on the specific mining source.

Field identification & locations

Identify by its waxy luster, conchoidal fracture, and slight translucency. It is common in Namibia, Turkey, and various locations in the western United States. Collectors look for uniform color and high translucency.