mineral

Blue Chalcedony

Silicon Dioxide (SiO2)

Hardness: 6.5-7 (Mohs scale), Color: Sky blue to grayish-blue, Luster: Waxy to vitreous (glassy), Crystal Structure: Trigonal (cryptocrystalline), Cleavage: None (conchoidal fracture), Specific Gravity: 2.58-2.64

Hardness: 6

Identified April 2, 2026More mineral →

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Physical properties

Formation & geological history

Formed through the deposition of silica from water in cavities or fissures in volcanic rocks (like basalt) or sedimentary environments. It is a microcrystalline variety of quartz.

Uses & applications

Used primarily as a gemstone for jewelry (cabochons, beads), decorative carvings, and in alternative healing practices. Historically used for making tools and seals.

Geological facts

In antiquity, chalcedony was used to make cylinder seals in Babylonia and Assyria. The name 'chalcedony' is believed to be derived from the ancient Greek town of Chalkedon in Asia Minor.

Field identification & locations

Identify in the field by its waxy luster, lack of visible crystals, and its ability to scratch glass. It often occurs in botryoidal (grape-like) masses or as nodules inside other rocks.