mineral

Blue Chalcedony

Silicon Dioxide (SiO2)

Hardness: 6.5–7 on Mohs scale; Color: Translucent to opaque pale blue, lavender, or grayish blue; Luster: Waxy to vitreous; Crystal Structure: Trigonal (cryptocrystalline); Cleavage: None; Specific Gravity: 2.58–2.64.

Hardness: 6
Color: Translucent to opaque pale blue, lavender, or grayish blue
Luster: Waxy to vitreous

Identified February 17, 2026More mineral →

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Physical properties

Formation & geological history

Formed from the deposition of silica-rich fluids in volcanic cavities (vesicles) or sedimentary environments at relatively low temperatures. It is a microcrystalline form of quartz. Specimens can range from prehistoric to modern geological ages depending on the host rock.

Uses & applications

Commonly used in jewelry as cabochons or beads, ornamental carvings, and by mineral collectors. It has historically been used for cylinder seals and amulets.

Geological facts

The name chalcedony is believed to come from the ancient Greek town of Chalkedon in Asia Minor. Unlike amethyst or citrine, its color is caused by the Tyndall effect—the scattering of light by microscopic inclusions.

Field identification & locations

Identify by its waxy luster, conchoidal fracture (glass-like breaking), and lack of visible crystals. It is commonly found in Turkey, Namibia, India, and the United States (notably the 'Ellensburg Blue' in Washington). To collect, look for rounded nodules or seam fillings in basaltic or sedimentary regions.