sedimentary
Botryoidal Chalcedony (Agate)
Silicon Dioxide (SiO2)
Hardness: 6.5-7 on Mohs scale. Color: Tan, brown, and translucent orange. Luster: Waxy to vitreous. Crystal Structure: Hexagonal (trigonal) microcrystalline. Features a 'grape-like' or botryoidal surface texture.
- Hardness
- 6
- Color
- Tan, brown, and translucent orange
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5-7 on Mohs scale. Color: Tan, brown, and translucent orange. Luster: Waxy to vitreous. Crystal Structure: Hexagonal (trigonal) microcrystalline. Features a 'grape-like' or botryoidal surface texture.
Formation & geological history
Formed through the deposition of silica from groundwater in cavities or veins within volcanic or sedimentary rocks. It often grows in concentric layers around a nucleus.
Uses & applications
Used primarily for lapidary work, jewelry (cabochons), and as a collector's specimen due to its unique bubbly texture.
Geological facts
The term 'botryoidal' comes from the Greek word 'botrys', meaning a cluster of grapes. This specific rounded shape is common in minerals that grow in confined spaces like vugs or pockets.
Field identification & locations
Identify in the field by its distinctive rounded, bubble-like surface and its high hardness (it will scratch glass). Commonly found in desert regions or areas with ancient volcanic activity.
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