mineral

Fairburn Agate

Cryptocrystalline Quartz (SiO2)

Hardness: 6.5-7 Mohs; Color: Multi-colored bands (reds, yellows, oranges, whites, greys); Luster: Waxy to vitreous; Crystal Structure: Trigonal/Monoclinic microcrystals; Cleavage: None (conchoidal fracture); Specific Gravity: 2.58-2.64

Hardness: 6
Color: Multi-colored bands (reds, yellows, oranges, whites, greys)
Luster: Waxy to vitreous

Identified May 9, 2026More mineral →

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Physical properties

Formation & geological history

Formed as ancient silica-rich groundwater deposited layers within cavities of limestone or volcanic hosts, primarily during the Pennsylvanian and Permian periods (approx. 250-300 million years ago), later weathering out into alluvial deposits.

Uses & applications

Highly prized as a state gemstone of South Dakota; used in lapidary work, jewelry, and by mineral collectors.

Geological facts

Designated as the South Dakota State Gemstone in 1966. They are world-renowned for their unique, sharp-angled 'fortification' patterns and vibrant color contrasts.

Field identification & locations

Identified by unique fortification banding and weather-worn 'holly-leaf' exterior texture. Primarily found in the Fairburn Agate Beds of the Black Hills/Badlands region in South Dakota and parts of Nebraska/Wyoming.