Agate

Physical Properties

Hardness: 6.5 - 7 on Mohs scale; Color: Pinkish-white with translucent banding; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.58 - 2.64

Formation & Geological History

Formed primarily in cavities of eruptive rocks or ancient lavas. Silica-rich fluids percolate through rock voids and deposit layers of chalcedony over thousands of years. Often found in volcanic host rocks dating back millions of years.

Uses & Applications

Used extensively in jewelry (cabochons, beads), decorative carvings, precision balances, and as ornamental stone in lapidary arts. Industrial use includes mortars and pestles for chemical testing.

Geological Facts

Agates often form in concentric circles resembling the rings of a tree. They were used by ancient civilizations for amulets and seals, and the famous 'Agate River' in Germany was a historical center for opal and agate cutting since the 15th century.

Field Identification & Locations

Identify by looking for waxy luster and distinct, translucent color banding. They are often found in gravel beds, dry river washes, or areas with historical volcanic activity. Brazilian and Lake Superior regions are famous locations.

Identified on: 5/10/2026

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