mineral

Chalcedony in Matrix

Silicon Dioxide (SiO2)

Hardness: 6.5-7 (Mohs scale), Color: White, translucent gray, or blue with tan/brown host rock, Luster: Waxy to vitreous, Crystal Structure: Microcrystalline/Trigonal (Cryptocrystalline), Cleavage: None/Conchoidal fracture, Specific Gravity: 2.6-2.64

Hardness: 6

Identified April 8, 2026More mineral →

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Physical properties

Formation & geological history

Formed from the deposition of silica-rich fluids at relatively low temperatures in cavities or fractures within volcanic rocks (basalt/rhyolite) or sedimentary formations. Commonly occurs during post-volcanic hydrothermal activity.

Uses & applications

Commonly used in lapidary work for making cabochons, beads, and carvings. Also used as an ornamental stone and collected as mineral specimens.

Geological facts

Chalcedony is actually a cryptocrystalline form of silica, composed of very fine intergrowths of quartz and moganite. Agate and Carnelian are both specific varieties of Chalcedony.

Field identification & locations

Identify in the field by its waxy luster, conchoidal (shell-like) fracture, and the fact that it cannot be scratched by a steel knife. It is frequently found in arid regions, riverbeds, and volcanic outcrops.