mineral

Blue Chalcedony

Silicon Dioxide (SiO2)

Hardness: 6.5–7 on the Mohs scale; Color: Pale blue, greyish-blue, or lavender; Luster: Waxy to vitreous; Crystal structure: Trigonal (cryptocrystalline); Cleavage: None; Specific gravity: 2.58–2.64.

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

Identified March 25, 2026More mineral →

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Physical properties

Formation & geological history

Formed from the deposition of silica-rich groundwater in cavities of igneous rocks such as basalt, often at low temperatures. It can also form in sedimentary environments. Geological age varies by deposit location.

Uses & applications

Predominantly used as a gemstone for jewelry (cabochons, beads), decorative carvings, and as a popular specimen for mineral collectors and holistic practitioners.

Geological facts

Chalcedony is a cryptocrystalline form of silica, meaning its crystals are too small to be seen even under a normal microscope. It has been used for seals and jewelry since at least the Bronze Age in the Mediterranean.

Field identification & locations

Identify by its waxy luster, translucency, and lack of visible crystals. It is often found in volcanic regions, riverbeds, and beaches. Look for botryoidal (grape-like) habits in the field.