mineral

Botryoidal Chalcedony (Druzy Quartz)

Silicon Dioxide (SiO2)

Hardness: 6.5-7 on Mohs scale; Color: Tan, beige, or milky white; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microcrystalline); Cleavage: None; Specific Gravity: 2.58–2.64

Hardness: 6
Color: Tan, beige, or milky white
Luster: Waxy to vitreous

Identified March 5, 2026More mineral →

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Physical properties

Hardness: 6.5-7 on Mohs scale; Color: Tan, beige, or milky white; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microcrystalline); Cleavage: None; Specific Gravity: 2.58–2.64

Formation & geological history

Formed through the deposition of silica from groundwater in cavities of volcanic or sedimentary rocks. The rounded 'grape-like' shapes (botryoidal) occur as silica layers build up over a central nucleus or surface.

Uses & applications

Used primarily in lapidary work for cabochons, jewelry, and as decorative mineral specimens for collectors. In industry, high-purity silica is used in glassmaking and electronics.

Geological facts

The word 'botryoidal' comes from the Greek word 'botrys', meaning a bunch of grapes. This specific specimen shows a 'druzy' coating, which refers to the tiny, sparkling crystals on the surface of the larger rounded forms.

Field identification & locations

Identify in the field by its rounded, bubble-like surface and hardness (it will scratch glass). Commonly found in geodes, volcanic vugs, and desert environments like the Southwestern US, Morocco, and Brazil.

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