mineral

Chalcedony Geode (Botryoidal Agate)

Silicon Dioxide (SiO2)

Hardness: 6.5-7 Mohs; Color: Translucent white to milky waxy gray; Luster: Vitreous to waxy; Crystal structure: Trigonal/Microcrystalline; Cleavage: None; Specific Gravity: 2.58-2.64

Hardness: 6
Color: Translucent white to milky waxy gray
Luster: Vitreous to waxy

Identified June 26, 2026More mineral →

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Physical properties

Hardness: 6.5-7 Mohs; Color: Translucent white to milky waxy gray; Luster: Vitreous to waxy; Crystal structure: Trigonal/Microcrystalline; Cleavage: None; Specific Gravity: 2.58-2.64

Formation & geological history

Formed through the deposition of silica-rich groundwater in cavities of igneous rocks or sedimentary host rocks. This specific specimen shows botryoidal (grape-like) growth and a geode-like cavity formed over thousands of years.

Uses & applications

Primarily used for lapidary work, jewelry (cabochons), and as a decorative collector's specimen. In industry, high-purity cryptocrystalline quartz is used in precision instruments.

Geological facts

Chalcedony is a cryptocrystalline form of silica, meaning its crystals are so small they can only be seen under high magnification. Botryoidal forms like this one occur when minerals grow around a central nucleus in radiating clusters.

Field identification & locations

Identify by its waxy luster, conchoidal fracture (breaks like glass), and inability to be scratched by a steel knife. Common in volcanic regions and desert washes where silica concentration is high.

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