sedimentary
Agate (Chert/Chalcedony)
Cryptocrystalline Quartz (SiO2)
Hardness: 6.5-7 on Mohs scale; Color: Gray, brown, white with translucent banding; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microscopic); Cleavage: None; Specific Gravity: 2.58-2.64
- Hardness
- 6
- Color
- Gray, brown, white with translucent banding
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Gray, brown, white with translucent banding; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microscopic); Cleavage: None; Specific Gravity: 2.58-2.64
Formation & geological history
Formed in cavities of volcanic rocks or sedimentary formations where silica-rich groundwater precipitates in layers. Common in ancient riverbeds and glacial deposits.
Uses & applications
Used in jewelry, decorative ornaments, lapidary art, and industrially for mortar and pestles due to its hardness.
Geological facts
Agate is a variety of chalcedony characterized by its fineness of grain and brightness of color. It has been used for over 3,000 years, dating back to Ancient Greece.
Field identification & locations
Identify in the field by its translucent edges, waxy texture, and unique banding patterns. Commonly found in riverbeds, lake shores (like the Great Lakes), and volcanic areas.
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