I spent years in Wyoming working at the Geological Survey (WGS) on the University of Wyoming campus. For vacations, I worked for various companies searching for mineral deposits all over North America. And after I left the geological survey, I consulted for other mining companies. Since I am familiar with Wyoming, let's first talk about the land of Cowboys and Cowgirls. Wyoming has a large variety of minerals and rocks and was a place where new discoveries were made nearly every year from 1977 to 2006. But since 2006, its been very, very quiet. Why?
|Discovery of a|
multi-billion gold deposit in Alaska.
Using traditional prospecting methods to search for other diamond deposits, some companies and the WGS identified hundreds of mineral anomalies. These are typically found by panning for diamond-indicator minerals - rare minerals brought up in rare volcanic eruptions from 90 to 120 or more miles from the upper mantle of the earth. One of the more prominent diamond-bearing volcanic pipes is known as kimberlite pipes. First identified in South Africa, kimberlite is the principal host for commercial diamond deposits. Once kimberlitic indicator minerals are identified from panning in streams, one simply follows the anomaly upstream until they run out of indicator minerals. At that point, we look upslope for some kind of anomaly that may be a depression, a vegetation anomaly, etc. While mapping and prospecting in known kimberlite and diamond fields (such as Iron Mountain, Middle Sybille Creek, State Line and elsewhere), I found a few kimberlites by searching for depressions, vegetation anomalies, carbonate rich blue ground soils (reacts to weak hydrochloric acid) in granitic and gneissic terrains, geophysical anomalies, and by following structural alignments of known kimberlites.
|Distinct depression near the Kelsey Lake diamond mine in |
Colorado. There is also a vegetation anomaly associated with
this kimberlite pipe (higher stands of grass) known as the
All these discoveries (with the exception of the Arkansas pipe) can all be attributed to the efforts and optimism expressed by Dr. Daniel N. Miller (RIP), who was the State Geologist and Director of the Wyoming Geological Survey (WGS) at the University of Wyoming. Dr. Miller and a couple of prospectors named Frank Yaussi, and Paul Boden, were the only people who felt there were possibilities that some of the kimberlite pipes in Wyoming and Colorado had more than just micro-diamonds. While searching for gold in Colorado near the Sloan kimberlites, Frank found many diamonds in his gold sluice, but no one at Colorado State University would give him the time of day and just ignored him (Frank Yaussi, personal communication, 1980). Then Paul Boden from Saratoga, Wyoming found a couple of excellent octahedral diamonds in the Medicine Bow Mountains, and again, no one at the University of Wyoming seemed to care (Paul Boden, personal communication, 1977).
|The Boden diamonds from the Medicine Bow|
Dr. Miller jump-started the diamond industry in North America. He provided some funding to his Minerals Section at the WGS to begin to evaluate the Wyoming deposits, and soon attracted me to his staff, as well as two mining companies - Cominco American and Superior Minerals to search for diamonds in the Colorado-Wyoming State Line district. Superior Minerals, with company CEO, Hugo Dummet, tested for diamonds at the Sloan 1 and 2 kimberlites in Colorado, while Cominco tested some Wyoming kimberlites after building a diamond mill in Fort Collins. Years later, Hugo was appointed head of BHP and invested in the great Ekati diamond mine in Canada, with its 156 diamondiferous kimberlite pipes! After the Ekati discovery, many other diamond deposits were found in Canada - but the US exploration more or less died.
Gold in the Rattlesnake Hills, Wyoming
What makes this area so significant is the presence of a Archean greenstone belt fragment. 'Greenstone belts' have been equated to 'Gold belts' in some cratons in the world, such as those in Africa, Australia and Canada. Greenstone belt rocks are mostly anomalous in gold; thus, if there is a way to mobilize the gold by hot hydrothermal fluids and geological methods for concentrating the precious metal in chemically favorable rocks or traps (ore shoots) developed during structural deformation, there is a possibility of forming significant to major gold deposits. So, here we have part of an exposed greenstone belt in the Rattlesnake Hills that is more than 2.5 billion years old. It's been intruded by several, much younger, Tertiary age (65 to 2.6 million years old) igneous intrusives that provided heat and mobilized gold and fluids from the intruded rocks. The belt is highly fragmented by deformation during the Laramide orogeny, so, all of the necessary requirements for a major gold deposit are there. I put these ideas together in 1981 after sampling another significant gold deposit in the Seminoe Mountains greenstone belt earlier in 1981 where a found some specimens with visible gold, received some highly anomalous assays including a mine dump sample that assayed 2.87 opt Au, and a banded iron formation sample with more than 1.0 opt Au. This area in the Seminoe Mountains also had distinct alteration zones from hydrothermal fluids. It is hard to believe, but I found most of these deposits and dozens of other gold anomalies prior to 1985 with an assay budget of only $100/year! As a comparison, mining companies typically spend hundreds of thousands and even millions of dollars on sampling, assaying, and drilling. Just take a look at Oak Island - and that's not even a mining company. And the company that the WGS originally contracted for assays, typically charged about $30/sample. Its a miracle I found anything.
Several other discoveries were made by the WGS during mapping projects in the historic mining districts at South Pass (Hausel, 1991), Seminoe Mountains (Hausel, 1994), Sierra Madre (Hausel, 1986), Laramie Mountains (Hausel and Hausel, 2011) and Medicine Bow Mountains (Hausel, 1989, 1993). In addition to these lode discoveries, prospectors and treasure hunters found many gold nuggets with metal detectors. For example, a 7.5 ounce nugget was found at South Pass by a Wyoming prospector. Another treasure hunter from Ft. Collins found more than 100 nuggets at South Pass, and a prospector from Arizona recovered 399 nuggets in the Sierra Madre (Hausel and Sutherland, 2000).
|A 7.5 ounce gold nugget found by prospector at|
Besides gold and diamonds, other metals and gemstones occur in Wyoming. In 1995, a significant platinum, palladium and nickel anomaly with associated copper silver, gold and silver in the Puzzler Hill area of the Sierra Madre near Saratoga (Hausel, 1997; 2000).
|pyrope garnets and emerald-green chromian diopsides from|
Butcherknife Draw, Wyoming
Another attractive gemstone discovered in 1998 in Wyoming is referred to as iolite, also known as cordierite and water sapphire. This led to a world-class discovery, first with spectacular iolites I found at Palmer Canyon, then with some iolite gemstones that potentially weigh more than a ton, at Grizzly Creek. But then I was able to find gem-quality iolite also at the Sherman Hills in the Laramie Mountains. This latter site is mostly unexplored, but based on trenching of cordierite around world war II, this latter Sherman Hills-Raggedtop deposit could host more than a trillion carats of the gemstone! The gem, known as iolite (gem-quality cordierite), is transparent, violet to deep blue (Hausel and Sutherland, 2000; Hausel, 2014). I found the easiest way to search for iolite is to look for areas that contain aluminum-rich (amphibolite-grade) metamorphic rocks such as kyanite schists, cordierite schists and andalusite schists and then start looking for some attractive glassy gemstones that are blue to purple in color.
|Rhodolite (pyrope garnet) faceted from rough material I|
collected in the Green River Basin of Wyoming.
|Youngite agate breccia|
|Blue forest agate (courtesy of Wayne Sutherland|
|Copper ore, Ferris-Haggarty mine|
|Schematic cross-section of|
a classical kimberlite pipe and
feeder dike complex
|Kelsey Lake diamond mine - photo by W. Dan Hausel|
|Wyoming jade (nephrite) with quartz crystals|
|Gold from South Pass. Photo by W. Dan Hausel|
|The author (GemHunter) stands in middle of photo at the base of Zirkel Mesa in the Leucite Hills|
wearing white field hat.
|Gold from Douglas Creek, photo by W. Dan Hausel|