mineral

Blue Chalcedony

Silicon Dioxide (SiO2)

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

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

Identified March 25, 2026More mineral →

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Physical properties

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

Formation & geological history

Formed through the deposition of silica from water in cavities of volcanic and sedimentary rocks. Its characteristic blue hue often comes from the Rayleigh scattering of light by microscopic inclusions. Most deposits range from Tertiary to Cretaceous in age.

Uses & applications

Primarily used in jewelry as cabochons, beads, and carvings. Also popular as a pocket stone for collectors and in metaphysical practices as a 'stone of calm.'

Geological facts

Known as a 'cryptocrystalline' variety of quartz, meaning its crystals are too small to be seen even under a microscope. Historically, it was used in the ancient Mediterranean to carve seals and amulets because it does not stick to hot wax.

Field identification & locations

Identify in the field by its waxy luster, lack of cleavage, and translucent 'milky' appearance. Common locations include Namibia, Turkey, India, and the United States (California/Oregon). It often appears as smooth, water-worn pebbles in alluvial deposits.