Botryoidal Chalcedony

Physical Properties

Hardness: 6.5-7 (Mohs scale); Color: White, translucent to waxy; Luster: Vitreous to waxy; Crystal structure: Trigonal (cryptocrystalline); Cleavage: None; Specific Gravity: 2.58-2.64

Formation & Geological History

Formed through the precipitation of silica from groundwater in the cavities of volcanic or sedimentary rocks, often in hydrothermal environments.

Uses & Applications

Commonly used as a gemstone for jewelry, in lapidary work for carvings, and as a popular specimen for mineral collectors.

Geological Facts

The term 'botryoidal' comes from the Greek word 'botrys', meaning a bunch of grapes, referring to its rounded, globular external form. Chalcedony is a cryptocrystalline form of silica, meaning its crystals are too small to be seen without high magnification.

Field Identification & Locations

Identified by its 'grape-like' bubbles and waxy surface. It is commonly found in basalt cavities (geodes) or as a replacement mineral in wood and fossils. Collectors look for pieces with high translucency or unique surface patterns.

Identified on: 5/15/2026

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