This is a Fairburn agate, a type of Fortification Agate with sharp bands of beautiful chalcedony colored red with trace minerals.

Agates typically form as nodules within a host rock as superheated silicates invade cavities, settle, and then cool. Layer after layer, these deposits form unique shapes and patterns with vibrant colors. The process of agatization can be applied to nearly any host formation, including fossils though more typically it occurs in volcanic or metamorphic rocks.

As you might expect, agates come in innumerable varieties. They are usually named for their location and the process of their formation.

This particular agate comes from "Teepee Canyon" near Custer, South Dakota. It was formed as a part of the Minnelusa Formation, a Late Carboniferous deposit from 300,000,000 years ago.

The agates were previously held by a private museum in Custer, South Dakota for many decades and recently deaccessioned. The area is now closed to new mining making these particular specimens rarer still.

As shown, the specimen exhibits the classic Fairburn patterns. We have several different agates available, each with rich colors running from bands of reds, browns, and orange to blue, black, yellow, and white. You can see all currently available agates at the collection below.

This specimen will ship in a sturdy carton and will also include a full-size Mini Museum Certificate of Authenticity.

Fairburn Agates are a rare example of Fortification Agate, a type of agate characterized by sharp-edged bands that resemble castle fortifications viewed from above. Their distinctive bands of chalcedony are colorized by trace minerals such as iron oxide and hematite (along with many others).

Fairburn’s have wide and distinctive bands. They take their name from the town of Fairburn, South Dakota. They are held in high regard by collectors and are the official state gemstone of South Dakota.

The individual, gem-quality specimens in the Mini Museum collection come from “Teepee Canyon” (also known as Hell’s Canyon). The Minnelusa Formation limestone in this region dates to the Late Carboniferous Period (Pennsylvanian) and Early Permian Period, roughly 300,000,000 years ago. At that time, the land known today as South Dakota was covered by a shallow sea.