sedimentary
Agate
Silicon Dioxide (Chalcedony), SiO2
Hardness: 6.5 to 7 on the Mohs scale. Color: Variable, often banded with white, gray, blue, yellow, or brown. Luster: Waxy to vitreous. Crystal structure: Trigonal (microcrystalline quartz). Cleavage: None. Specific gravity: 2.58 to 2.64.
- Hardness
- 6
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5 to 7 on the Mohs scale. Color: Variable, often banded with white, gray, blue, yellow, or brown. Luster: Waxy to vitreous. Crystal structure: Trigonal (microcrystalline quartz). Cleavage: None. Specific gravity: 2.58 to 2.64.
Formation & geological history
Formed mainly in cavities of volcanic rocks or ancient lavas through the deposition of silica from groundwater solutions, often over millions of years.
Uses & applications
Used in jewelry, ornamental carvings, polished specimens for collectors, and historically for precision instruments.
Geological facts
Agate is one of the most common materials used in art carving and was highly valued in ancient civilizations like Ancient Greece and Egypt for seals and rings.
Field identification & locations
Found worldwide, particularly in Brazil, Uruguay, India, and parts of the USA. Identified by its banded patterns and waxy luster.
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