sedimentary

Agate (Chert/Chalcedony)

Cryptocrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

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

Identified May 31, 2026More sedimentary →

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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.