mineral

Chalcedony (Quartz Nodule)

Silicon Dioxide (SiO2)

Hardness: 6.5-7 on Mohs scale. Color: Tan, brownish-orange, translucent. Luster: Waxy to vitreous. Crystal structure: Cryptocrystalline (microscopic quartz fibers). Cleavage: None (conchoidal fracture). Specific gravity: 2.6-2.64.

Hardness: 6
Color: Tan, brownish-orange, translucent
Luster: Waxy to vitreous

Identified April 11, 2026More mineral →

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Physical properties

Formation & geological history

Formed through the precipitation of silica from groundwater in volcanic or sedimentary cavities (vugs). This specific specimen appears to be a stream-tumbled or weathered nodule, likely from the Cenozoic era, though quartz can be any age.

Uses & applications

Used primarily for ornamental stone-working, lapidary (cabochons), and collection. In industry, high-purity silica is used for making glass and electronics.

Geological facts

Chalcedony is a cryptocrystalline form of silica, meaning its crystals are too small to be seen without extreme magnification. This 'lumpy' or botryoidal shape is typical for silica that fills empty spaces in host rock.

Field identification & locations

Identify in the field by its waxy appearance, extreme hardness (it will scratch glass and steel), and lack of visible crystal faces. Commonly found in gravel beds or near volcanic outcrops.