sedimentary
Agate
Silicon Dioxide (Chalcedony), SiO2
Hardness: 6.5 to 7 on the Mohs scale; Color: Varies widely including grey, white, brown, blue, red, and yellow, often with banded patterns; Luster: Waxy to vitreous; Crystal structure: Trigonal (microcrystalline quartz)
- Hardness
- 6
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5 to 7 on the Mohs scale; Color: Varies widely including grey, white, brown, blue, red, and yellow, often with banded patterns; Luster: Waxy to vitreous; Crystal structure: Trigonal (microcrystalline quartz)
Formation & geological history
Formed mainly within cavities of volcanic and metamorphic rocks through the deposition of silica from groundwater solutions over millions of years
Uses & applications
Used in jewelry, decorative ornaments, lapidary art, and historically for precision instruments like mortar and pestles
Geological facts
Agate is a variety of chalcedony that typically forms concentric bands in lovely multicolored patterns. Ancient civilizations valued it for amulets and seals.
Field identification & locations
Identified easily by its distinctive waxy luster, conchoidal fracture, and characteristic banding when chipped or cut. Found worldwide, particularly in regions with past volcanic activity.
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