Wednesday, October 9, 2013

Gold Deposits Near Cheyenne, Wyoming

Prospect in the vicinity of the Copper King mine, Wyoming
When I began working for the Wyoming Geological Survey, we were a relatively productive government agency in charge of unraveling the geology associated with mineral deposits as well as  in charge of finding new mineral deposits. But, we were one of the smallest agencies in the State: a very sad commentary for a state that makes its living off mining and oil and gas resources. In addition, our salaries were just one step above that of a custodian.

Not only was most of the legislature uninterested in the State's mineral resources, but I found many at the University of Wyoming were also anti-mining. This is a very strange concept particularly since the University of Wyoming and many of the professors owed their jobs and existence to the mining and oil and gas industries. But even educated professors are under the assumption that money grows on trees.

During the first couple of years I worked at the Survey, I was asked to assist in building a Childrens' Museum in downtown Laramie - it was going to have a geology theme. I donated rocks and assisted in building a mine tunnel for the kids to walk through and on the outside of this exhibit, one board member requested we put on a simple pie diagram to show kids and parents how important mining and oil and gas was to the state. It was a pie diagram showing ad valoreum taxes to the state. Whoa - was this a bad idea.
hydrothermal alteration mineral assemblages found in the Silver Crown district, Wyoming.
One of the board members, a flaming liberal from the university, demanded that the pie diagram be modified to show mining, oil and gas were not important - she demanded we make up statistics to fit her agenda! "Mining can't be important she exclaimed - it's bad for the environment and attracts dirty people". I mentioned they were dirty because they have to work for a living (unlike her) and mention mining was also referenced in the Holy Bible, and no where did it indicate mining was a bad profession - remember the Golden Fleece? This was a sheep skin used in a sluice to extract gold. As I suspected, she was not into the Bible. Most extreme liberals have never heard of the Bible or any facts.

Visible gold is seen in rock sample adjacent to brassy pyrite in
this sample from the Copper King
That was one of the first times I saw science taking it in the shorts for politics - and this was 30 years ago. I finally quit working at the Children's Museum when the rest of the board sided with the liberal and modified the pie diagram to show mining and oil and gas contributed little to the state. I didn't want to be associated with lies - but over the years, I found this was characteristic of people with political agendas from the state geologist, to the governor, to the president.

When I left the Wyoming Geological Survey, they actually had a Chinese and Russian communist on the staff and a director who thought the US Constitution was made only to control others, and had nothing to do with him. Now why did some of my friends give up their lives in Vietnam?

How did I get onto that subject? Ah, I know, I was thinking about the time I worked on the Copper King property while at the WGS. Over the years, I developed a fascination with different mining districts, and one of my favorites was the Silver Crown district. At one time I had planned to do a detailed study of the hydrothermal alteration patterns at the Copper King mine and acquired drill core from the US Bureau of Mines. I was hoping to find money to pay for thin sections and microprobe analyses, when the director decided the core (several $million worth of core) was collecting dust and without warning, he transported all of the core on a weekend to the city dump.
Stockworks at the Copper King
In spite of this and other set-backs, I was able to spend time on the ground at the Silver Crown district and at the Copper King mine and was able to map the accessible underground mines in the district (Hausel and Jones, 1982) and over the years, I spent time researching the mineralization and alteration at the Copper King mine and nearby properties (Hausel, 1997). It became clear to me that the Copper King was a deeply eroded core of a Proterozoic age gold-copper porphyry system and over the years when I had exploration geologists and company CEOs visiting my office on the UW Campus while they were searching for ideas for gold mines, I told many that this was one of my top picks for a commercial gold deposit. Some of these people listen, and it was picked up time and time again. But like most commercial gold deposits, development awaits the right alignment of the stars.

Most people are under the impression when a commercial gold (or other metal or gemstone) deposit is found, it is "Eureka" and then the mining begins. Unfortunately, that never happens except in the movies. "Mines are made, they are not found" was stated at some talk I attended at the Northwest Mining Convention many years ago. It takes the right circumstances, people, investments, government support, etc, etc, etc. Take a look at the Pebble deposit in Alaska. A prophyry deposit so large that it dwarfs the Bingham Canyon deposit in Utah. Can you imagine finding a $100 billion deposit and no one can figure out how to make a mine out of it?  I can. We found a $60+ billion gold deposit at Donlin Creek Alaska in 1988, and no one can figure out how to make a mine out of it yet. I found a gold district in Wyoming in 1981-1982 at the Rattlesnake Hills that likely has $5 to 10 billion in gold, and again, no one can make a mine out of it.
Pervasive propylitic altered quartz monzonite
The Copper King mine near Cheyenne, was drilled by the US Bureau of Mines (one of the few productive government agencies that met its demise under Clinton and Gore because it didn't fulfill their political agenda of making things greener - so thousands of government employees were terminated, valuable research ended, all because a few politicians wanted to promote global warming whether fact or fiction) and several different exploration companies. Today, it is reported the property has a gold equivalent resource of 2 million ounces in gold and copper. Hey, now someone should be able to put that kind of property in production especially since it is sitting adjacent to I-80 and just down the road from Cheyenne. Access is good.

And it is apparent that the deposit is bigger - based on exploration and drilling - it is open in every direction (except up, maybe). That's right, drilling has yet to find the limits of the ore deposit. However, the ore appears to end to the east - or does it?  I recently mapped a fault and found that the footwall on the east side had down dropped - how far down is anyone's guess at the moment, but it needs to be drilled to find out if the mineralization continues in that direction. I would be very surprised if it does.
Look at the massive sulfide in the valley in the center of the photo. Also, note the old boiler. If you look close, you can see
that it ruptured along the seam.

Then there is the problem of having similar anomalies in the area. Terry Klein of the USGS pointed out that there were similar hydrothermal anomalies nearby, and I worked on another I found that appears to be very large, but could not map the anomaly due to private land access problems. 

Yes, its a silly looking hat. But in Wyoming, even the
Gem Hunter needs to be warm.
Remember I mentioned that the deposit doesn't appear to continue up in the sky. When I misled you as considerable erosion has occurred in this area since the Proterozoic. So, large amounts of gold are likely sitting in conglomerates and streams - including some that drain into Cheyenne. Can you imagine that - placer gold in downtown Cheyenne.

References Cited

Hausel, W.D., and Jones, S., 1982, Geological reconnaissance report of metallic deposits for in situ and heap leaching extraction research possibilities: Geological Survey of Wyoming Open File Report 82-4, 51 p.
Hausel, W.D., 1997, The geology of Wyoming's copper, lead, zinc, molybdenum, and associated metal deposits: Geological Survey of Wyoming Bulletin 70, 224 p.

Tuesday, May 18, 2010

The Copper King Mine, Wyoming - two million ounce deposit

Photo of Hecla Mill, JE Stimson Collection
The Copper King mine (NW section 36, T14N, R70W) was mapped and sampled by the author and others in the past. The Copper King (Arizona) mine was located in 1881 and developed by the Adams Copper Mining and Reduction Company. The property was later worked by the Hecla Mining Company.

All that remains of the old Hecla mill is a rock foundation on the side of the
This property has a 2 million ounce gold equivalent of gold-and copper associated with shears, faults, veins, veinlets and stockworks in granodiorite and quartz monzonite that have distinct propylitic and potassic hydrothermal alteration mineral assemblages similar to younger copper-gold porphyry deposits. The geology also suggests that the ore deposit could be expanded. That's right, the eastern flank of the Copper King was down-faulted. So what lies under the Tertiary cover in that area?  Hopefully, drilling and geophysics will resolve that question in 2013 or 2014.

The Copper King is considered one of the five best gold deposits in Wyoming and is likely the root zone of a deeply dissected Proterozoic age porphyry gold-copper deposit.

A shaft was sunk 157 feet with 102 feet of crosscuts on the 80-foot level, and 260-feet of drifts and crosscuts and three large rooms on the 130-foot level. A 100-foot adit was driven near the shaft but stopped short of intersecting the shaft. Some ore was shipped, although the total amount of production is unknown (Ferguson, 1965).

Photo of Hecla smelter located across the road
from the Silver Crown Mill, Ferguson Archives.
The Copper King is a deeply dissected Proterozoic age copper-gold porphyry deposit with disseminated sulfides and stockworks surrounded by propylitic and potassic alteration zones. Fourteen samples collected by Jamison (1912b) varied from 0.22% to 2.43% Cu, 0.06 to 0.42 opt Au, and 0.4 to 0.8 opt Ag. Mineralization at the surface occurs as malachite and chrysocolla: at depth as chalcopyrite, pyrite, minor bornite, pyrrhotite and native copper (McGraw, 1954; Soule, 1955).

Potassic alteration of granodiorite at the Copper King.
Primary hypogene mineralization was intersected during drilling to a depth of 150 to 180 feet by the Bureau of Mines. The primary ore is overlain by an oxidized and leached cap extending from the surface down to depths of 30 to 150 feet (Soule, 1955). Near the Copper King shaft, a zone of intense silicification consists of intersecting quartz veins and veinlets. Extending out from the shaft is a zone of potassium silicate alteration expressed by secondary enrichment of biotite and microcline-quartz intergrowths with some muscovite, sericite, epidote, and sulfides. This potassic altered zone is enclosed by a propylitic altered zone consisting of secondary chlorite and epidote with sulfides (Hausel and Jones, 1982b).

The available drilling data indicate that the maximum metal concentrations were on the order of 1.5% Cu and 0.2 opt Au (Klein, 1974). Drilling by the U.S. Bureau of Mines showed mineralization continued to a depth of at least 1,024 feet. Spectrographic analyses showed traces of lead, zinc, tungsten, and 0.5 to 3.0% TiO2 (Soule, 1955). An estimate of the in situ ore reserves were made by Nevin (1973) based on drilling:
Tons                  Cu                           Au                                  Stripping ratio
(millions)          (%)                         (opt)                                    (waste/ore)

2.8                   0.36                         0.044                                          0.5
6.0                   0.32                         0.038                                          1.2
13.5                 0.26                         0.028                                          1.8
35.0                 0.21                         0.022                                          2.0

In 1987, Caledonia Resources leased the mine to test as a large-tonnage, low-grade, disseminated gold deposit. The company reported preliminary gold estimates on the order of 4.5 million tons of ore averaging 0.044 opt Au (or about 200,000 ounces of contained gold). Sampling suggests the deposit has a minimum strike length of 600 to 700 feet with a 300 foot width that is open at depth (Stockwatch, 1987). More recent data by Compass Minerals expanded the gold-copper resource. The company reported a gold resource of 23 million tons of ore grading at 0.82 grams or essentially 770,000 ounces of contained gold, while Paso Rico Resources indicated the deposit to contain a million ounce equivalent gold-copper resource (Hausel, 2008a). More recent work by Saratoga Gold Mining Company outlined a 2 million ounce equivalent ore deposit containing 1.2 million ounces of gold and considerable copper. And based on mapping by the author, it is likely that this resource will be expanded.

Photo of the interior of the Hecla mill near Cheyenne
Wyoming. JE Stimson Collection, University of Wyoming.
Geochemical and geophysical anomalies suggest the known resource could be increased. For example, a large magnetic anomaly (1,000 ft wide x 2,000 ft long, 450 gamma magnitude), almost identical to that reflected by the Copper King deposit (800 ft wide x 1,500 ft long, 500 ft gamma magnitude) was identified in a gravel covered area 4,500 feet to the southeast. Soil samples over this anomaly returned anomalous values for the pathfinder elements mercury, zinc, and arsenic supporting the presence of hidden mineralization. Geological and geophysical evidence also suggests the presence of sulfides down plunge to the southwest and to the east of the Copper King. An IP (induced polarization) survey identified a moderate to shallow metal factor anomaly trending east-northeast of the principal mineralized area (Klein, 1974).

Mineralized terrains showing location of Silver
Crown district in southeastern Wyoming.

Aerial photo showing location of the Copper King mine

  Will the Copper King ever be mined? If a reasonable mining plan and royalty can be negotiated with the State of Wyoming, the answer is 'yes'. The deposit is mostly on State land which is beneficial. If it were on public lands, the Federal Government would tie this property up in their bureaucratic network until any mining company would give up due to the mountains of paperwork.

The author (Gem Hunter) back at the Copper King
mine in 2012.
Over 30 years, I explored Wyoming and mapped most of the hardrock mining districts and found a few deposits with very favorable geology that needed to be explored further. Besides the Carissa Mine and the Rattlesnake Hills gold deposits, the Copper King was one of the top gold deposits in the state that I felt would be mined with higher gold prices. Today, we have those high gold and copper deposits and with further exploration, I would not be surprised to see this deposit surpass the 2.5 to 3 million ounce equivalent.

What really surprises me is there are other mineral deposits (including gold) sitting at a number of locations in Wyoming - some with surprising size that are being ignored by industry and the State. Some are worth $millions, others $billions and at least one might be worth $hundreds of billions.

Maybe its time to go Gold Prospecting, Diamond Prospecting or Gemstone Prospecting in Wyoming.

Geological map of the Silver Crown district

I found it!!!  Yes, the two-million ounce gold deposit at Copper King has even more ore. I
was able to follow and map a fault that offsets the eastern edge of the ore deposit by dropping
it down to the east. This means, there is more ore to be found under a blanket of gravel. How
much more? Need to drill to find out.