mineral

Botryoidal Chalcedony

Silicon Dioxide (SiO2)

Hardness: 6.5-7 (Mohs scale), Color: White to bluish-gray, Luster: Waxy to dull, Crystal Structure: Hexagonal (cryptocrystalline), Cleavage: None, Specific Gravity: 2.58–2.64

Hardness: 6

Identified May 9, 2026More mineral →

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Physical properties

Hardness: 6.5-7 (Mohs scale), Color: White to bluish-gray, Luster: Waxy to dull, Crystal Structure: Hexagonal (cryptocrystalline), Cleavage: None, Specific Gravity: 2.58–2.64

Formation & geological history

Formed by the low-temperature deposition of silica from groundwater in the cavities of igneous or sedimentary rocks, often resulting in this characteristic 'bunch of grapes' (botryoidal) texture.

Uses & applications

Used primarily as a decorative specimen for collectors, in lapidary work for cabochons and beads, and historically for making stone tools due to its conchoidal fracture.

Geological facts

The term 'botryoidal' comes from the Greek word 'botrys', which means a bunch of grapes. Chalcedony is the cryptocrystalline form of quartz, meaning its crystals are too small to be seen with a normal microscope.

Field identification & locations

Identify in the field by its bubbly, rounded surface texture and waxy luster. It will scratch glass but cannot be scratched by a steel knife. Common in volcanic regions and inside geode cavities.