mineral

Seam Agate

Agate (Banded variety of Chalcedony, SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 (Mohs scale); Color: Variegated bands of white, orange, brown, and grey; Luster: Waxy to vitreous; Crystal Structure: Trigonal (Microcrystalline); Cleavage: None (Conchoidal fracture); Specific Gravity: 2.58-2.64.

Hardness: 6
Color: Variegated bands of white, orange, brown, and grey
Luster: Waxy to vitreous

Identified June 20, 2026More mineral →

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Physical properties

Formation & geological history

Formed as secondary deposits where silica-rich groundwater fills cracks, fissures, or seams in host rocks (often volcanic or sedimentary). The banding represents successive layers of mineral deposition over thousands of years.

Uses & applications

Commonly used for lapidary work, jewelry (cabochons), ornamental carvings, and as a popular collector's item due to its unique patterns when sliced and polished.

Geological facts

Unlike pocket agates which form in rounded geodes, seam agates form in flat veins or sheets. The specific specimen shown appears to be a 'fairburn-style' or 'fortification' agate seam with intricate zigzag banding.

Field identification & locations

Identify in the field by looking for translucent, banded veins cutting through darker host rock. It is often found in areas with historical volcanic activity or in sedimentary gravel beds. Common in the Western US, South America, and Africa.