Thursday, June 28, 2012

Gold Processing & Extraction While Bear Hunting


Visible gold in goethite and quartz,
Mary Ellen Mine. (Steve Gyorvary specimen).
If you decide to mine lode gold, you can keep it simple and dig for specimen-grade gold samples from veins and breccias. Although such samples with visible gold are rare and more valuable than the price of gold, if you have the right vein or ore shoot, they are worth pursuing. When ever you see gossans or tawny to brown limonite and goethite in quartz - look for visible gold! Gossans are something prospectors need to learn to recognize. 

If you decide to mine your lode using open pit or underground methods - you will need deep pockets to pay for mining as well as permitting. In this case, it may be easier to start looking for a company that has the expertise and deep pockets.

Detrital gold is by for the best type of gold to search for as a prospector as it has already been mined by Mother Nature, and now it is up to you to figure out how to concentrate it. To extract placer (detrital) gold from a creek using a gold pan (not recommended as it will wear out your back), sluice, trommel, dredge or some other concentrating equipment, you will likely need permits from the State or Feds. The government is totally out of touch when it comes to permitting, as in most cases they will try to permit you to death. Some states may even require a permit to operate a gold pan on public property even though this would be as absurd as requiring a permit to operate a fork in a restaurant; however, Democrats were actually talking about this when I left Wyoming. One of the easiest ways to find out rules and regulations for prospecting in your state is to join a local prospecting club. Many gold prospecting clubs are associated with the Gold Prospectors Association of America: and there are independent groups such as the Wyoming Prospectors Association. 

GRIN AND BEAR IT! And don't forget to support the NRA, unless you are willing to prospect grizzly country without a gun. Just imagine, panning in Wyoming, Montana, Alaska or even Washington DC and you look up just in time to see a grizzly licking its chops while staring at you 50 feet away. Sure, you can use that brand of bear repellant spray your university professor recommended even though he/she/it has never seen a grizzly except on TV. 

In the woods, a bear can easily sneak up to you, particular when it sees you are listed in the specials on the menu. Remember, it can charge as fast as 35 mph! But, you have that handy, dandy spice, errr, repellant in your pocket or back pack. How fast can you get that vial out of your back pack? "Oh, there it ...." "CHOMP".  

If you are lucky, you may have a little more than a second to get that thing out of your pocket, get the cap off, point and squirt, but I'll bet you end up served on the dinner special. That 700 to 1,500 pound grizzly can cover a short 50-foot distance in .... can you believe 1 second! Don't believe me, you can do the math yourself. And if you are lucky enough to point and shoot your little spice vial. I imagine that  bear mass, with all of its kinetic energy, is not going to stop easily - "splat and chomp!" 

So, the next time your hike and bike Berkeley professor tells you to use repellent, remember he/she/it is thinking about human sacrifice to keep the bears well fed. But if you have a gun, particularly a very large gun (12 gauge), 44 or 45 cal., you may stand a chance. But, why not a 357 magnum? Well, because one of our geologists in Alaska shot a typical, everyday, meat-loving black bear in-between the eyes at point blank range as it was trying to eat another geologist. All it did was give the bear a nasty headache. It knocked the bear down, but then it got up, and ran off until the next day, when it decided to come back looking for another geology snack.

GOLD PANNING POLLUTION. When I was in Wyoming, there was a faculty member in the  Geology Department who thought gold panners were polluting Douglas Creek in the Medicine Bow Mountains. Obviously, she never tried to operate a gold pan herself, otherwise she would not have made such a ridiculous statement.  Gold panning is a real, serious, pain in the neck (as well as the back and especially, the lower back). 
Gold Panning in the Medicine Bow Mountains, Centennial
Ridge district.
No one found gold at what was known as the
Mother Lode, but some found nice specimens of pyrite
(fool's gold)
 and some found almandine and pyrope garnet!
Pyrope garnet is a tracer 
mineral for finding diamonds!
So, somewhere upstream
there is an eroding diamond pipe
leaking pyrope garnet (and maybe diamonds) into
 the creek.

Years ago, I met two prospectors from Lander Wyoming who were working Smith Gulch at South Pass while I was mapping the greenstone belt and old mining districts, and they were recovering about 20 ounces of gold per week. At 1600/ounce, that's only about $32,000 per week. Not bad for two guys.

Often we get use to seeing gold pans filled with gold - this does not really happen in real life; so when we see gold filled pans, remember, the gold was found with some other equipment and placed in the pan for a photo opt.

Panning is an easy - it just takes a little confidence and a couple of pans full of sand and mud, and soon you will be an expert. Gold has a very high specific gravity (15 to 19.3), which means you are going to have to make an serious effort to wash gold out of your pan. So put a little effort into your panning. If you are ending up with a tablespoon or two of what is known as black sand (mostly magnetite with a few minerals such as ilmenite, zircon, etc), with specific gravities around 4 to 5, you are doing good. But be assured, you probably did not wash out much gold as it is 3 to 4 times heavier by volume, than those black sands. 

Stamp mill at Goldfields, Arizona
While panning for diamonds in California, we recovered a gemstone known as benitoite near Poker Flat and chromian diopside from serpentinite in northern California (Hausel, 1996). In Wyoming, we panned many gem-quality garnets, some diamonds, and numerous sapphires and rubies and found dozens of localities where gold had not been reported before (including the Laramie City landfill!) (Hausel and others, 1994). In samples panned in the Laramie Mountains near Vedauwoo, we found fluorite (easy to recognize in black sands - it is purple in this area and crushes easily) and many samples with chromian diopside and pyrope garnet near Eagle Rock. This suggests there are undiscovered diamond pipes! 

While searching for evidence of diamond pipes, we found distinct, small, structurally-controlled vegetation anomalies including one at (41o17'39.96"N; 105o22'46.95"W) along the edge of Eagle Rock. This same area has several beaver ponds to the northwest, any of which could be hiding diamond pipes.

Not too far from Eagle Rock, we identified other possible diamond pipes that remain a mystery. These included the Bowling Pin Anomaly (41o11'15.39"N; 105o19'34.67"W), a circular depression with carbonate in soils that had a couple of bowling pins in the depression. The entire area has many such anomalies including the HJ17 depression (41o12'01.92"N; 105o19'10.46"W). Further south (actually just south of the interstate) we identified 42 highly suspicious cryptovolcanic structure of which anyone of them could be a kimberlite (diamond) pipe. All of these anomalies remain untested due to various access problems.

Arrastra gold concentrator. This was a very primitive grinder with large rocks
attached to a pivot at the center. A mule would walk around in circles pulling
a lever that would continue to drag the boulders over a trough where gold-
bearing quartz would be placed to be crushed.
Other minerals of interest found while panning include a lot of white material that was impossible to pan out. It was too heavy! So I stuck it under a black light and with short-wave ultraviolet light, it exhibited strong, blue fluorescence - it was scheelite (a tungsten ore)! This was recovered from samples (along with gem-quality iolite) near the old strong mine along the 9th street road in the Laramie Mountains.

And what else did we find? At one location in extreme northwestern Colorado, 4 diamonds, 17 rubies and 24 pyrope garnets were panned. Wow, what a find! Actually, this was the site of the historical 1872 diamond hoax fraud which occurred near what is now called Diamond Peak. This diamond scam was amazing as it was an outcrop that was salted in 1871 and 1872 and the crooks scammed US Senators (first time in history that scam artists scammed scam artists). 

A primitive roller mill displayed at the Douglas Museum, Jerome, Arizona.
Eric Hausel stands adjacent to the mill.

References Cited

Hausel, W.D., 1991, Economic geology of the South Pass granite-greenstone belt, Wind River Mountains, western Wyoming: Geological Survey of Wyoming Report of Investigations 44, 129 p.

Hausel, W.D., 1996, Pacific Coast diamonds-an unconventional source terrane in Coyner, A.R., and Fahey, P.L., eds., Geology and ore deposits of the American Cordillera, Geological Society of Nevada Symposium Proceedings, Reno/Sparks, Nevada, p. 925-934.
Hausel, W.D., and Stahl, S., 1995, The great diamond hoax of 1872: Wyoming Geological Association Resources of Southwestern Wyoming Guidebook, p. 13-27.
Hausel, W.D., Marlatt, G.G., Nielsen, E.L., and Gregory, R.W., 1994, Study of metals and precious stones in southern Wyoming: Geological Survey of Wyoming Open File Report 94-2, 61 p.


Gold from Douglas Creek Wyoming. Photo shows gold recovered with the black sands removed (the penny is just used for scale). To remove black sands, simply wait until your panned concentrates are dry. Get a large and strong magnet, cover it with a paper towel and slowly sweep over the concentrates - whamo - nearly all of the black sands will be removed. What you have left is a little gold, garnets, mica and if you look close, you may even find diamond indicator minerals such as pyrope garnet, chromian diopside, picroilmenite, chromite and/or diamond. Diamond has a specific gravity of 3.5 and will often end up in the black sand concentrates. Much of the lighter colored material will be removed during panning: most of which will be quartz with a little feldspar. Quartz has a specific gravity of only 2.7.

Mining on Douglas Creek using a long tom and a
dredge on a rotating platform with shovel.