Chalcedony (Botryoidal)

Physical Properties

Hardness: 6.5-7 (Mohs scale); Color: White, grayish-white, to pale yellow; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None; Fracture: Conchoidal; Specific Gravity: 2.6-2.64.

Formation & Geological History

Formed through the precipitation of silica from low-temperature hydrothermal fluids or groundwater in cavities of volcanic or sedimentary rocks. This specific habit is botryoidal (grape-like) or sugary microcrystalline crusts.

Uses & Applications

Used as semi-precious gemstones in jewelry (beads, cabochons), ornamental carvings, and widely collected as mineral specimens. In industry, it was historically used for making stone tools due to its hardness and chip patterns.

Geological Facts

Chalcedony is a cryptocrystalline form of quartz. The name probably comes from the ancient Greek town of Chalkedon in Asia Minor. It is the base mineral for varieties like agate, jasper, onyx, and carnelian.

Field Identification & Locations

Identify by its waxy luster, hardness (will scratch glass), and bubbly botryoidal surface texture. Look for it in volcanic regions or as 'desert roses' in arid environments. Often found in geodes or linings of rock cavities.

Identified on: 5/17/2026

Mode: Standard