1. Looking towards the NW, please describe the coloration of the
different levels of the limestone shelf from top to bottom. How
thick are the different layers and how do you think they were they
formed?
2. What is the main composition of the Teepee Canyon agate and how
long ago did the process begin?
3. In order to complete this hands on task, it will require a
measuring device. You must locate a Teepee canyon agate nodule and
measure it for data purposes. Any unit of measurement will suffice.
Also please describe the nodule that you have found (shape,
texture, color etc….). The nodule can be in any kind of
condition or size. Refer below for more information and the
reference photographs of an actual agate nodule.
General Information: Teepee canyon is located in the
southern Black Hills near the Wyoming border. It is east of
Newcastle Wyoming and west of Custer and the Jewel Cave National
Monument. Take Highway 16 to FS road 456. Parking coordinates
provided below. From the gate to the parking area is .46 miles and
from the gate to the EC is .54 miles. The sign at the gate says
that the road is closed between Nov 1-May 15. However, foot travel
is still allowed when the gate is closed for the season. Depending
on weather conditions the road can be rugged, so do not attempt to
drive the family wagon to the parking area. It is only a half mile
hike in on the FS road gate. Please stay on the FS road as no off
road travel is permitted.
History: It is rumored that during the late 1800’s,
General Custer led an expedition of men to this location. From atop
the ridge he looked down and saw hundreds of teepee’s in the
canyon below, hence the name. The Teepee Canyon agate was mined for
many years on claims. Through the 1980’s activities at these
mines declined as the owners grew past retirement age. The area was
closed for development of new mining plans prior to the early
1980’s. In recent years, activity has been limited to only
surface collection by agate hunters.
On August 24, 2000 the area was devastated by a large forest fire.
Named the Jasper Fire, it burned a total of 85,508 acres. It burned
nearly 90% of the land area of Jewel Cave National Monument. Due to
the hot , dry conditions and an abundance of fuel on the forest
floor, the fire spread very quickly. In the first day the fire
consumed an average of 7 football fields of forest per minute.
Subsequent exploration after the fire led to numerous agate areas
located within a 5 mile radius of Teepee Canyon. These areas were
not known before due to the thick vegetation and the fire has now
opened up new areas for agate hunting. A decade later you can still
see the evidence of the devastating fire.
The Geology: The Teepee Canyon Agate is a close relation
to the famous Fairburn agate found in the Kern agate beds near
Fairburn SD. Fairburn Agates are found along riverbeds and washes
where erosion has occurred, but the Teepee agate is found incased
in limestone and is formed in nodules and must be hand mined. The
Teepee Canyon agates are found 3 feet deep into the limestone
layer. Both of these agates have the trademark holly leaf
fortification banding and this is what sets these agates apart from
the rest. Fairburn agates come in all different colors, but the
Teepees are reddish-orange, yellow, and white with calcite, drusy
quartz or amethyst centers. The matrixes are large and usually show
a dull-tan color. As you approach the fortifications, a milk
chocolate-colored jasper is common. Some of the nodules found do
not contain any colorful banding and only contain the reddish
colored Jasper. This is due to not having the right mixture of
minerals and the conditions needed over millions of years to form
these agates. The Teepee Agate is 98% Silica (SiO2), a combination
of Silica and oxygen. The balance being trace minerals which help
provide the color.
Much like the Fairburn agate, the Teepee Canyon agate began the
journey 300 million years ago in a shallow sea that once covered
western South Dakota. Teepee agates 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 Teepee agates were formed.
These agates laid buried until the Black Hills uplift occurred
60-70 million years ago. Volcanic activity in what is now known as
the northern hills area forced upwards 15,000 feet of rock into a
domed formation. For another 30 million years after the event,
there were many episodes of erosion and ash falls taking place
shaping the Black Hills. Most of the Black Hills looks very similar
to what it once did 30 million years ago. When at the EC location
there is still evidence of the seas that once existed 300 millions
years ago, as fossilized sea life can still be found imbedded into
the limestone.
Forest Service Regulations:This Earthcache is strictly
for collecting scientific data for logging this Earthcache. I am
posting the rules and regulations of the area so that you are aware
of them. The rules by the Black Hills National Forest Service state
that off road travel in this area is forbidden, so please stay on
the FS road. 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.”
For more information on agate hunting and the geology of the
Black Hills area please refer to the books Fairburn Agate-Gem of
South Dakota by Roger Clark, Midwest Gem Trails by June Zeitner and
Roadside Geology of South Dakota by John Paul Gries.