Some of My Favorite Places to Walk

I discovered the pleasures of walking at South Pass after I first sunk my field vehicle in a bog near the old ghost town of Lewiston in 1985. It was quite impressive (not the walk, but the vehicle): only the windows and roof were visible.

The South Pass region is part of an Archean (>2.5 billion year old) granite-greenstone belt with several old gold mines and a few ghost towns. It might even be a great place mountain bike (although I prefer to use a motorcycle), as large portions of the belt are accessible by dirt and graded roads. But take several tire patches, intense folding and deformation resulted in most rock units sitting on end. The sharp rock edges are tough on the tires.

To get there, drive 30 miles south of Lander along Highway 28. Just before reaching the turnoff to Atlantic City and South Pass City, you will see a spectacular, man-made lake on the west side of the highway – this was the Atlantic City iron ore open pit mine, which operated in the 60s and 70s and closed in 1983. Whoever said mines were ugly, not only had no imagination, but also never saw this mine.

South Pass consists of rolling hills on a gradual sloping pediment (Figure 1). Near the foothills, you will be about 8,500 feet above sea level where a portion of the granite-greenstone terrain lies within the national forest. Keep your eyes open in this area for beryl associated with granite pegmatites. About 20 years ago, a Lander resident found a spectacular gem-quality aquamarine that weighed a few thousand carats in the Anderson Ridge area.

Much of the terrain is a high semi-desert administered by the Bureau of Land Management, which maintains two fee campgrounds near Atlantic City. South Pass gradually slopes to the south and east, reaching a low of 7,200 feet above sea level near the Sweetwater River, where one will find sparse grass, sagebrush, and prickly pear cactus along south-facing slopes. Sagebrush, grass, willow, aspen, and pine are found on some north facing slopes and creek valleys in the region. Only a few creeks including the Sweetwater River are perennial: most other creeks and gulches tend to dry by August.

As you tour the greenstone belt, you will find evidence of old ghost towns and several old gold mines (Figure 2). Take sunblock, hiking shoes, a gold pan, and snowshoes. While mapping the greenstone belt, I was buried under a foot of snow on June 25th, 1985. You will find good use for a gold pan in the creeks (Figure 3) - this is a historic gold district. If you are interested in a geological tour of the area, plan to tag along on a field trip listed on our website http://wsgsweb.uwyo.edu/metals/. Or take along one of the following geologic and mining history guides (these are available through the Wyoming State Geological Survey’s (WSGS) publication office, and can be ordered over the phone (307/766-2286).

Guide to the Geology and Mineralization of the South Pass Area: WSGS Reprint 49, 20 p., by W.D. Hausel and J.D. Love, 1991.

Tour Guide to the Geology and Mining History of the South Pass Gold District, Fremont County, Wyoming: WSGS Public Information Circular 23, by W.D. Hausel, 1984.

Economic Geology of the South Pass Granite-Greenstone Belt, Wind River Mountains, Western Wyoming: WSGS Report of Investigations 44, 129 p. (includes a 1:48,000 scale geological map of the greenstone belt) by W.D. Hausel, 1991.

Snowy Range Scenic Byway and Medicine Bow Mountains, Southeastern Wyoming

The Snowy Range Scenic Byway in the Medicine Bow Mountains of southeastern Wyoming can be visited by driving west from Laramie and east from Saratoga to Highway 130. After you leave a day of canoeing or fishing along the North Platte River near Saratoga, or visiting the University of Wyoming campus in Laramie, a day hike in the high mountainous region of the Medicine Bow Mountains can be a nice change. There are many good places for day hikes.

Spectacular rock faces of Proterozoic quartzite and metaconglomerate form a backdrop for scattered alpine lakes making this a must for camera buffs (Figures 5, 6). If you know where to look, you’ll see some excellent Proterozoic stromatolites and some spectacular folds near the Mullen Creek-Nash Fork shear zone. This is also a great place for an encounter with a moose, or a herd of Elk.

Take your gold pan, and keep your eyes open for diamonds – a few diamonds have been found in the area in the recent past, and diamond indicator minerals are not uncommon. The Medicine Bow Mountains are riddled with prospects and mines, particularly in some of the lower elevations near Douglas Creek to the south. A great place for a day hike if you enjoy old mining districts is the Centennial Ridge district just outside the village of Centennial. Several old gold and platinum mines are scattered along this ridge, and good specimens with visible gold are periodically found on mine dumps (Figure 7). Again, look at our website for information on an upcoming field trip to the district, or just take a copy of:

Guide to the Geology, Mining Districts, and Ghost Towns of the Medicine Bow Mountains including the Snowy Range Scenic Highway: WSGS, Public Information Circular 32, 53 p., by W.D. Hausel, 1993.

Kirwin Mining District, Wood River area, Absaroka Mountains, Northwestern Wyoming

The Kirwin Mining district lies within the Absaroka Mountains along the eastern margin of Yellowstone National Park. Access is by the Wood River trail, 33 miles southwest of Meeteetse, Wyoming (Figure 8). Take a backpack and some good shoes. You will also be in bear country, so take some pepper spray. This deeply dissected plateau is cut by numerous streams and rivers surrounded by steep mountains formed primarily of Tertiary volcanic rock. You should be in good shape for this hike as you have several miles of hiking before you reach Kirwin, but it is all along the Wood River trail.

The Kirwin district is underlain by a large, copper-silver porphyry that was initially prospected in the 1800s for silver, copper, and lead. Some of the old lode mines in the area still yield some spectacular silver specimens (Figure 9). For instance, channel samples collected at some mine faces by AMAX in the 1960s and 1970s assayed at more than 100 ounces/ton of silver, which makes one wonder why more mining didn’t occur in the district. In the 1960s and 1970s, Kirwin was a target for open pit mining by AMAX, which had identified a major porphyry copper deposit lying under Bald Mountain near the old ghost town of Kirwin (Figure 10).

Little remains of the old ghost town, but several old mines can still be seen in the area. Some publications you might want to take along include:

The Kirwin Mineralized Area, Park County, Wyoming: WSGS Preliminary Report 2, 12 p., by W.H. Wilson, 1964.

The Geology of Wyoming's Copper, Lead, Zinc, Molybdenum, and Associated Metal Deposits in Wyoming: WSGS Bulletin 70, 224 p., by W.D. Hausel, 1997.

General Geologic Setting and Mineralization of the Porphyry Copper Deposits, Absaroka Volcanic Plateau, Wyoming: Wyoming Geological Association 33rd Annual Field Conference Guidebook, p. 297-313, by W.D. Hausel, 1982.

Sweetwater Rocks, Granite Mountains, Central Wyoming

The Granite Mountains in central Wyoming provide an impression of an old mountain range submerged in a sea of young (Tertiary) sediments. Some of the rocks in this ancient craton are reportedly as old as 3.6 billion years.

This is a great place to hike if you like to search for mineral specimens – just take lots of water to drink. Drive along Highway 287 north of Rawlins, or east of Lander, until you run into Jeffrey City. From Jeffrey City, you will need to go north across the Sweetwater River. You may get the impression that you just drove into the outback of Africa or Australia, but there will be no kangaroos in site.

Just a little west of Jeffrey City, the Graham Ranch road will take you into some very interesting areas. This is one of my favorite places to hunt for rubies, sapphires, jasper, and jade (Figure 11). A few years ago, I found one low-quality ruby that was 2.5 inches long. Many other rubies were found nearby in an outcrop that was mapped over a length of 5,000 feet. Several spectacular jade specimens have been found in this region, some weighing more than 200 pounds (Figure 12). A good guide to the area is:

The Tin Cup District, Central Wyoming - A Rock Hound's Paradise. International California Mining Journal, v. 65, no. 8, p. 65-68, by W.D. Hausel, 1996.

List of Figures

Figure 1. View from the B&H mine. The rolling hills in the background are underlain by metamorphosed graywacke, basalt and gabbro.
Figure 2. View of the historic Miners Delight mine near the Miners Delight ghost town.
Figure 3. Take your gold pan with you. This gold was recovered from Rock Creek, east of Atlantic City.
Figure 4a. A pot of gold may lie under the Duncan headframe. South Pass has several old mines similar to the Duncan. While hiking in the area, watch for the precious metal as nearly every year someone reports finding some nice gold specimens.
Figure 4b. View of the historic Duncan headframe and miners hotel.
Figure 5. Quartzite cliffs of the Snowy Range (photo by Ray Harris).
Figure 6. View of the Snowy Range with alpine lake in foreground.
Figure 7. The Platinum City mine dump viewed form the top of Centennial Ridge.
Figure 8. The Wood River valley is spectacular and scenic.
Figure 9. The Wolf mine is one of several old mines in the Kirwin district.
Figure 10. Bald Mountain at Kirwin is part of an extensive porphyry copper-silver deposit. In the early 1980s, AMAX drilled an estimated 196 million tons of geological reserves containing low-grade copper and molybdenum with associated values in silver, gold, titanium, lead, and zinc.
Figure 11. Apple green jade from Granite Mountains (photo by Dave Freeman).
Figure 12. Large boulder of Wyoming jade found near Jeffrey City. This 218-pound boulder of gem-quality jade now resides on permanent display at the Wyoming State Geological Survey Building on the University of Wyoming campus in Laramie (photo by Ray Harris).

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