Mineral variant

Botryoidal Chalcedony (Desert Rose / Agate)

Silicon Dioxide (SiO₂)

Hardness: 6.5-7 (Mohs scale); Color: Gray, blue-gray, black, or tan; Luster: Waxy to vitreous; Crystal Structure: Hexagonal (Microcrystalline); Cleavage: None (Conchoidal fracture); Specific Gravity: 2.58-2.64.

Hardness: 6
Color: Gray, blue-gray, black, or tan
Luster: Waxy to vitreous

Identified February 21, 2026More mineral variant →

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Physical properties

Formation & geological history

Formed through the deposition of silica-rich groundwater in cavities of volcanic or sedimentary rocks. The 'bubbly' botryoidal texture occurs as the mineral grows around a central nucleus, often during the Cenozoic era or more recent geological periods in arid environments.

Uses & applications

Used primarily by rock collectors, in lapidary work for cabochons or beads, and as decorative landscape stones. High-quality specimens are used in metaphysical circles and ornamental jewelry.

Geological facts

The term 'botryoidal' is derived from the Greek word 'botrys,' meaning a bunch of grapes. These specimens are often found in desert regions where volcanic activity once provided the silica and thermal fluids necessary for formation.

Field identification & locations

Identify in the field by looking for rounded, grape-like clusters on the surface of a rock that is too hard to be scratched by a steel knife. Commonly found in the American Southwest (Arizona, Nevada), Mexico, and Morocco. Look for 'vugs' or pockets inside weathered volcanic host rock.

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