1. What is the South Dakota state gemstone?
2. What is the South Dakota state mineral?
3. What is the main composition of the Fairburn agate?
4. What is the name of the limestone layer in which Fairburn Agates
were first formed?
5. Name 3 other minerals that can be found at the Fairburn Agate
beds?
6. In this location, where is the most concentration of rock and
minerals: Top of the bluff, sides of the earthen mounds or ground
level?
7. The Black Hills uplift occurred 70 million years ago in which
direction of the cache site?
General Information: The Fairburn Agate Beds are located
about 12 miles NE of the town of Fairburn in Custer County SD. Take
French Creek rd (Hwy 18) east off of Hwy 79 to the French Creek
Campground. The campground and agate beds are located in the
Buffalo Gap National Grassland.
These agates beds contain a vast array of rock and minerals with an
occasional fossil to be found. Rock collectors from all around the
world scour the landscape in search of the elusive Fairburn Agate.
Fairburn agates were first discovered in the early 1900’s
near the town of Fairburn and soon found there way into local area
rancher's collections. The Fairburn Agate are the most coveted of
all agates due to there colorful banding and rarity. Even though
they are now getting scarce, they can still be found as erosion
occurs.
The picturesque landscape consists of cedar topped bluffs and large
multi-colored earthen mounds scattered with rock. The terrain is
challenging and the weather unpredictable, but that adds to the
essence of the adventure. You may park at the campground and hike
in or you may drive a 4X4 vehicle to the location. A 4X4 is highly
recommended and DO NOT drive the NG road in wet conditions as the
ground turns into a clay like substance and can be very
slippery.
The primary area where Fairburn agates are found is in a wide band
just outside of the Black Hills to the east and south. Extending
from a point east of Rapid City, through the Badlands National
Monument, and along the White River and Cheyenne River breaks into
NW tip of Nebraska.
The Geology: The Fairburn agate are most identified by
there colorful and sharp holly leaf banding. These fortification
agates come in a variety of mixed colors such as red, blue, purple,
brown, white, black, yellow, pink and orange. Each Fairburn agate
has it’s own unique characteristics. The composition of the
Fairburn is usually 98% Silica (SiO2), a combination of Silica and
oxygen. The balance being trace minerals which help provide the
color.
Other agates can also be found in the agate beds such as prairie
agates, bubble gum agates and black agates. Though not as precious
as the Fairburn, they are still fun to find. Some of the minerals
that can be found in this area are rose quartz, milky quartz,
jasper, tourmaline, chalcedony, feldspar, mica.
The journey of the Fairburn Agate began 300 million years ago in a
shallow sea that once covered western South Dakota. Fairburns were
formed in the Minnelusa limestone layers at the bottom of the
shallow sea that was covering part of the continent of Pangaea.
Pangaea was once a super continent 250 million years ago, then
eventually split into several different continents. Silica began to
accumulate in the soft sediments at the bottom of the sea. The
Silica that was accumulating derived from meteoric waters eroding
from the land and from organisms accumulating at the bottom of the
sea as they died. The process occurred over millions of years, and
during the process some of the limestone was being replaced by
Silica and forming into nodules. When the conditions were right,
the nucleation of spherulitic crystals began in the form of fibrous
growths. Silica concentrations and trace minerals are how the
colorful banding on the Fairburn agates were formed. These agates
laid buried until the Black Hills uplift 60-70 million years ago.
The uplift of the Black Hills caused 7,500 feet of material to be
deposited. Once exposed to the surface these agates tumbled along
in streams being rounded chipped and shaped, sometimes taking
hundreds of years to make there journey. Once these agates made
there journey onto what is now the eastern slope of the Black Hills
they were once again buried in the Chadron formation layer for
another 30 million years. Geologic events to the west caused a
layer after layer of volcanic ash accumulation and therefore buried
the agates once again. As erosion began to carve out the Badlands
terrain, the Fairburns began to surface once again. Now they lay in
hiding, awaiting there next finder.
Additional Information: Both the South Dakota State
Mineral and Gemstone can be found in the Fairburn agate beds. The
state Mineral is Rose Quartz and the state gemstone is the Fairburn
agate. If you need any additional information on Fairburn agate
collecting be sure to check out these 2 books: Roger Clark -
Fairburn Agate Gem of South Dakota and June Zeitner- Midwest Gem
Trails. Also there is a rock shop located off Hwy 79 that is only
open during the summer where you can get additional
information-N43° 47.411 W103° 13.259
Rock hounding is allowed anywhere on the National Grasslands, with
some restrictions. Collecting on private land requires permission
from the owner. A permit is required for the collection of
vertebrate paleontological specimens, including their trace fossils
(tracks) on any federal lands. These permits are only issued for
scientific research and educational purposes. Restrictions with
rock hounding are as follows: the collection of any objects for
commercial purposes is prohibited: trading and bartering are
considered commercial activities. USDA, Forest Service policy and
guidance in 36 CFR, 261.9 states “The following are
prohibited: digging in, excavating, disturbing, injuring,
destroying, or in any way damaging to any prehistoric, historic or
archeological objects.”
FTF will receive an Earthcache Geocoin. When attempting FTF
please state the date and time at the cache site just in case there
are any discrepancies.
FTF Congratulations to: forgiven4ever Winner of the Earthcache
Geocoin