mineral

Chalcedony (Botryoidal/Tumbled Agate)

Silicon Dioxide (SiO2)

Hardness: 6.5-7 on Mohs scale; Color: Grayish-green to translucent brown; Luster: Waxy to vitreous; Crystal Structure: Trigonal (cryptocrystalline); Cleavage: None; Specific Gravity: 2.58-2.64

Hardness: 6
Color: Grayish-green to translucent brown
Luster: Waxy to vitreous

Identified March 29, 2026More mineral →

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Physical properties

Hardness: 6.5-7 on Mohs scale; Color: Grayish-green to translucent brown; Luster: Waxy to vitreous; Crystal Structure: Trigonal (cryptocrystalline); Cleavage: None; Specific Gravity: 2.58-2.64

Formation & geological history

Formed through the deposition of silica from groundwater in cavities of volcanic and sedimentary rocks. This specimen is water-worn or tumbled, likely originating from a riverbed or coastal environment.

Uses & applications

Used primarily in jewelry as cabochons, for ornamental carvings, and as a semi-precious gemstone for collectors.

Geological facts

Chalcedony is a cryptocrystalline form of silica, meaning its crystals are too small to be seen with a standard microscope. It has been used since the Bronze Age for making cylinder seals and jewelry.

Field identification & locations

Identify in the field by its waxy luster, conchoidal fracture, and translucency when held to light. Common in basaltic areas or as pebbles in gravel pits globally.

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