mineral

Chalcedony Nodule in Matrix

Silicon Dioxide (SiO2)

Hardness: 6.5-7 on Mohs scale; Color: Grayish-blue to milky white with iron oxidation; Luster: Waxy to vitreous; Crystal Structure: Microcrystalline/Cryptocrystalline (Hexagonal/Trigonal); Cleavage: None; Specific Gravity: 2.58-2.64

Hardness: 6
Color: Grayish-blue to milky white with iron oxidation
Luster: Waxy to vitreous

Identified March 18, 2026More mineral →

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Physical properties

Formation & geological history

Formed through the precipitation of silica from groundwater in cavities of volcanic or sedimentary rocks. This specific specimen appears to be a water-worn nodule embedded in a conglomerate or breccia-like matrix, likely from the Cenozoic era.

Uses & applications

Primary uses include lapidary work (jewelry, cabochons), ornamental carvings, and historically as tools/weaponry (flint). In industry, silica is used for abrasives.

Geological facts

Chalcedony is a cryptocrystalline form of silica, meaning its crystals are so small they can only be seen under high magnification. Agate and Carnelian are specific color varieties of chalcedony.

Field identification & locations

Identify in the field by its waxy luster, conchoidal (shell-like) fracture, and inability to be scratched by a steel knife. It is frequently found in riverbeds, coastal areas, or basaltic lava flows.