mineral

Blue Chalcedony

Chalcedony (SiO2)

Hardness: 6.5-7 (Mohs scale); Color: Pale blue, lavender-blue, or grayish-blue; Luster: Waxy to vitreous; Crystal structure: Hexagonal (trigonal) cryptocrystalline; Cleavage: None; Specific gravity: 2.58-2.64

Hardness: 6
Color: Pale blue, lavender-blue, or grayish-blue
Luster: Waxy to vitreous

Identified April 10, 2026More mineral →

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Physical properties

Formation & geological history

Formed through the deposition of silica from aqueous solutions in cavities of volcanic rocks (basalts) and sedimentary environments at relatively low temperatures.

Uses & applications

Primarily used as a gemstone in jewelry (cabochons, beads), decorative carvings, and as a popular specimen for mineral collectors.

Geological facts

Chalcedony was named after the ancient Greek town of Chalkedon in Asia Minor. It is a cryptocrystalline form of silica, meaning its crystals are too small to be seen without high magnification.

Field identification & locations

Identify in the field by its waxy luster, conchoidal fracture (smooth, curved breaks), and hardness (it will scratch glass). It is commonly found in Malawi, Namibia, Turkey, and various locations in the SW United States.