sedimentary
Agate
Chalcedony (SiO2)
Hardness: 6.5-7 on the Mohs scale; Color: Variable, often banded in white, gray, blue, red, brown; Luster: Waxy to vitreous; Crystal structure: Trigonal/Microcrystalline; Cleavage: None, exhibits conchoidal fracture; Specific gravity: 2.58-2.64
- Hardness
- 6
- Color
- Variable, often banded in white, gray, blue, red, brown
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5-7 on the Mohs scale; Color: Variable, often banded in white, gray, blue, red, brown; Luster: Waxy to vitreous; Crystal structure: Trigonal/Microcrystalline; Cleavage: None, exhibits conchoidal fracture; Specific gravity: 2.58-2.64
Formation & geological history
Formed mainly in cavities of volcanic and metamorphic rocks through the deposition of silica from groundwater solutions over millions of years.
Uses & applications
Used for making jewelry, ornamental objects, carvings, mortars and pestles for laboratory use, and highly prized by mineral collectors.
Geological facts
Agates are among the most popular stones used in lapidary art. The bands in an agate reflect the successive stages of deposition of silica in a cavity.
Field identification & locations
Easily identified by its characteristic concentric bands or translucent waxy appearance. Commonly found in regions with ancient volcanic activity worldwide, such as Brazil, India, Germany, and the US.
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