Botryoidal Agate / Chalcedony Geode

Physical Properties

Hardness: 6.5-7 on Mohs scale. Color: Translucent white, gray, and tan. Luster: Waxy to vitreous. Crystal Structure: Hexagonal (cryptocrystalline). Cleavage: None (conchoidal fracture).

Formation & Geological History

Formed via the deposition of silica from groundwater in cavities of igneous or sedimentary rocks. The rounded, grape-like shapes (botryoidal) grow outwards from nucleation points within a void.

Uses & Applications

Used primarily for lapidary work, jewelry making (cabochons), and as decorative cabinet specimens for mineral collectors.

Geological Facts

The term 'botryoidal' comes from the Greek word 'botrys', meaning a bunch of grapes. These specimens often form the interior lining of geodes or vugs.

Field Identification & Locations

Identify by the characteristic bubbly or rounded surface texture and waxy luster. Commonly found in volcanic regions or limestone deposits globally.

Identified on: 5/2/2026

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