mineral

Blue Chalcedony

Silicon Dioxide (SiO2) - Microcrystalline Quartz

Hardness: 6.5-7 (Mohs scale); Color: Pale blue, lavender-blue, 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-blue, or grey-blue
Luster: Waxy to vitreous

Identified March 15, 2026More mineral →

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Physical properties

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

Formation & geological history

Formed at low temperatures through the deposition of silica from groundwater in cavities of volcanic rocks, sedimentary layers, or fossilized wood. Most specimens date from the Tertiary period to the present.

Uses & applications

Mostly used in jewelry as cabochons, beads, and carvings. Also popular in the metaphysical community and for ornamental decor like bookends.

Geological facts

In antiquity, blue chalcedony was used to carve seals and amulets. It is named after the ancient Byzantine port of Chalcedon. Unlike crystalline quartz (like amethyst), its structure is so fine the crystals can only be seen under a microscope.

Field identification & locations

Identify by its waxy luster, conchoidal (shell-like) fracture, and translucent appearance. It lacks the visible grains found in quartzite. Common locations include Namibia, Turkey, India, and the Mojave Desert in the USA.

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