At any rate, South Dakota Fairburn Agates are “plains’ agates” mostly to the south and east of the Black Hills and mostly associated with terrace gravels along streams and/or conglomerate beds and lag deposits on top of the Eocene-Oligocene White River Group (Chadron Formation or perhaps the underlying Eocene Chamberlain Pass Formation). However, Fairburns or Fairburn-type agates have been located in the adjacent states of Wyoming and Nebraska. Buena Vista Gem Works (2013) noted that in Nebraska the area of collecting is north of US 20 from Chadron to the Wyoming state line, generally following outcrops of the Chadron. Major collecting localities in Wyoming include Lance Creek and Hat Creek (southwest and reasonably close to the Hills) and Glendo and Guernsey (further to the south). Gemworks (2013) also reported “stray finds” of Fairburn-type agates from the Yellowstone River in Montana, near New Raymer, Colorado, (northeast Colorado) and along the Yampa River in northwest Colorado. The Chadron crops out near New Raymer but is absent from the Yellowstone and Yampa River localities. Pabian and Cook (1976) reported Fairburn-type agates at localities along the east-flowing Platte River in Nebraska.
Most agate hunters describe Fairburns as fortification agates with a holly leaf banding. They have sort some of red to orange banding due to iron oxides with the black banding ascribed to manganese. The “type area” for Fairburns is near (east) of the small village of Fairburn along French Creek (see blog postings on 6-12-12and 8-19-12). It seems well established that the agates out on the South Dakota plains originated in the Minnelusa Formation of Pennsylvanian-Permian age and were transported away from outcrops in the Black Hills by Cenozoic streams. Perhaps the best-know site for observing in situ Fairburn agates is at Teepee Canyon west of Custer (see blog posting 8-18-12).
You know I saw her for the very first time
A pretty little girl standing all alone
Hey, pretty baby, can I take you home…
Dickinson, W.R., M.A Klute, M.J. Hayes, S.U. Janecke, E.R.Lundin, M.A. McKittrick and M.D. Olivares, 1988, Paleographic and Paleotectonic Setting of Laramide Sedimentary Basins in the Central Rocky Mountain Regions: Geological Society of America Bulletin, v. 100.
Sutherland, W.M., 1990, Gemstones, Lapidary Materials, and Geologic Collectables of Wyoming: Geological Survey of Wyoming Open File Report 90-9.