Chalcedony with Matrix

Physical Properties

Hardness: 6.5-7 (Mohs scale); Color: Grayish-blue, waxy white, translucent; Luster: Waxy to Vitreous; Crystal Structure: Cryptocrystalline (Trigonal); Cleavage: None (Conchoidal fracture); Specific Gravity: 2.6-2.64

Formation & Geological History

Formed from the deposition of silica-rich water in cavities or fissures within volcanic or sedimentary rocks at relatively low temperatures. Often found in geodes or as botryoidal masses within a rocky host matrix.

Uses & Applications

Used primarily for ornamental carvings, semi-precious jewelry (beads and cabochons), and as a collector's specimen. Historically used for making tools and seals.

Geological Facts

Chalcedony is a cryptocrystalline form of silica, meaning its crystals are so small they can only be seen under high magnification. It often serves as the base for semi-precious stones like agate, onyx, and carnelian.

Field Identification & Locations

Identify in the field by its waxy luster, translucency when held to light, and its ability to scratch glass but not be scratched by steel. Commonly found in volcanic regions or desert environments as weathering-resistant nodules.

Identified on: 5/4/2026

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