Rock Identifier
Botryoidal Chalcedony / Quartz (Silicon Dioxide (SiO2)) — mineral
mineral

Botryoidal Chalcedony / Quartz

Silicon Dioxide (SiO2)

Hardness of 7 on the Mohs scale. Colors range from white, cream, to vibrant orange/peach due to iron oxide inclusions. Luster is vitreous to waxy. Crystal structure is trigonal (microcrystalline quartz). It exhibits a distinct botryoidal (grape-like) habit with rounded, globular surface projections.…

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Physical properties

Hardness of 7 on the Mohs scale. Colors range from white, cream, to vibrant orange/peach due to iron oxide inclusions. Luster is vitreous to waxy. Crystal structure is trigonal (microcrystalline quartz). It exhibits a distinct botryoidal (grape-like) habit with rounded, globular surface projections. Cleavage is none, fracture is conchoidal. Specific gravity is approximately 2.65.

Formation & geological history

Formed through low-temperature hydrothermal or low-temperature ground water deposition, where silica-rich solutions fill cavities and fractures in host rocks, precipitating layer by layer in a spherical, bubbly form. Often found in volcanic air bubbles (vesicles) or sedimentary rock cavities.

Uses & applications

Used in lapidary arts, wire-wrapping, cabochons, and as collector specimens.

Geological facts

Botryoidal formations occur when multiple crystal nuclei grow outward simultaneously at the same rate, creating the characteristic rounded, bubbly appearance resembling a bunch of grapes.

Field identification & locations

Easily identified by its distinct rounded 'bubble' texture and hard, quartz-like composition. Commonly found in areas with past volcanic activity or weathering limestone geodes. Collectors look for unique colors and intact, undamaged botryoidal clusters.