mineral

Blue Chalcedony

Chalcedony (Silicon Dioxide, SiO2)

Hardness: 6.5-7.0 (Mohs scale), Color: Pale blue to bluish-grey, Luster: Waxy to vitreous, Crystal Structure: Trigonal (Cryptocrystalline), Cleavage: None, Specific Gravity: 2.58-2.64

Hardness: 6

Identified July 10, 2026More mineral →

Explore Blue Chalcedony in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Hardness: 6.5-7.0 (Mohs scale), Color: Pale blue to bluish-grey, Luster: Waxy to vitreous, Crystal Structure: Trigonal (Cryptocrystalline), Cleavage: None, Specific Gravity: 2.58-2.64

Formation & geological history

Formed via the deposition of silica from aqueous solutions, typically in cavities of igneous rocks such as lava. It is a cryptocrystalline variety of quartz composed of very fine intergrowths of quartz and moganite.

Uses & applications

Commonly used as a gemstone for cabochons, beads, and ornamental carvings. It is also a popular collector's item in tumbled form.

Geological facts

Unlike macrocrystalline quartz like amethyst, chalcedony is made of microscopic crystals. The blue color is often the result of the Tyndall effect, where light is scattered by colloidal-sized particles.

Field identification & locations

Identified by its waxy luster and translucency. It is common in Turkey, Namibia, and the USA. Collectors look for consistency of color and lack of inclusions.