mineral

Chalcedony (Botryoidal)

Silicon Dioxide (SiO2)

Hardness: 6.5–7 on Mohs scale; Color: White to grayish-blue, often translucent; Luster: Waxy to dull; Crystal structure: Trigonal/Monoclinic (Microcrystalline); Cleavage: None; Specific gravity: 2.58–2.64.

Hardness: 6
Color: White to grayish-blue, often translucent
Luster: Waxy to dull

Identified April 7, 2026More mineral →

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Physical properties

Formation & geological history

Formed from the deposition of silica-rich fluids at low temperatures in cavities of other rocks, particularly volcanic and sedimentary ones. It typically exhibits a botryoidal (grape-like) growth pattern.

Uses & applications

Used widely in lapidary work for cabochons, carvings, and jewelry. It is also a popular specimen for rock hounds and mineral collectors due to its unique textures.

Geological facts

Chalcedony is a cryptocrystalline form of silica, meaning its crystals are too small to be seen without high magnification. Famous varieties include agate, carnelian, and onyx.

Field identification & locations

Identify in the field by its waxy luster, smooth rounded surfaces (botryoidal texture), and extreme hardness (will scratch glass). Commonly found in desert regions, riverbeds, and volcanic outcrops.