Between the Bighorn Area and Prior Mountains is the deposit of this fine agates.
The agates do have a sedimentary formation. They occur in septarias in shale. Since the 1960ies at this location comercial agate-mining took place. In the last few years it was possible for privat agate-collectors to dig for agates against paying a fee. In the year 2008 the mining stopped.
The agates are showing characteristical colours in red, yellow and pink tones. The banding they are showing is wide and soft, not such a fine-lined pattern that agates from vulcanic origin do poseed.
The pattern is a very vivid fortification - caused sometimes by inclusions of the matrix.