Tuesday, June 6, 2017

Prospecting for Gemstones

Some years back. The author in his lab
at the University of Wyoming
I searched for gemstone deposits in Wyoming, something that was nearly unknown in the cowboy state, other than jade and some agates. The more I looked, the more I found, and then I began to uncover geological clues to other deposits.

Found more gemstone deposits and previously unknown minerals in Wyoming, than any other person in history. More than anyone should have been able to do. But, I had developed some good prospecting models for finding gold and gemstone deposits - some worked, others didn't. Some methods were so simple - such as simply looking at the quality of the minerals - if they were translucent to transparent, or had interesting colors, they were unique? Sounds simple, but no one paid attention to mineral quality until after I began finding one deposit after another - some adjacent to highways and even along the interstate. The only other person to look for gem characteristics in minerals was Dr. J.D. Love of the US Geological Survey! Why? Well it likely goes back to education. In geology, we are not taught to look for gems - it's that simple. And instead of calling peridot "peridot", geologists call it "olivine".

Then there are gemologists - sure they can recognize gems, but they have no idea how to find them in the field and few have any idea what they look like in nature since they rarely see raw gemstones. So, the education system for geologists and gemologists has this one major flaw that worked in my favor. So, do you think universities bothered to correct this flaw? I offered to teach a class in prospecting for gemstones and gold and the Geology Department told me it would be a very popular class, but politics made it impossible! Politics!

One of more than a thousand publications
produced by the author
Take for instance the discovery of the first gem-quality peridot in Wyoming. I was actually searching the Leucite Hills near Rock Springs for evidence of a near surface, buried, olivine-rich lamproite pipe similar to those in Western Australia at Ellendale and Argyle where some of the more attractive fancy diamonds in the world are found and mined. In 1986, the Geological Survey was operated by a competent director who asked the legislature for a special appropriation to send me to Western Australia to study the newly discovered diamond pipes.

Three things I brought back from that conference - they have jack rabbits that are much taller with pockets, the people all speak funny, and the newly discovered diamond deposits were found in olivine lamproite - not kimberlite. And guess who had the largest lamproite field in North America? That's right - Wyoming! And as time progressed, it was another project I placed on my 'to do' list.

One of my finest achievements - I nearly drank as much
beer as half of the prospectors in the Atlantic City
Mercantile - and also published this book on South Pass
So, after I returned from the International Kimberlite Conference in Australia, I went back to work mapping Wyoming's principal gold district - the 500-square mile South Pass greenstone belt near Lander. I don't want to get into a discussion on greenstone belts at this point, but you can read about them at wikipedia. So, in 1991, I finished the South Pass greenstone belt, published numerous papers on the subject, published eight 7.5 minute quadrangles showing the geology of the district, wore out a few pairs of field boots, tipped several beers with the locals at the Atlantic City Mercantile, mapped 3 dozen underground mines, and published a summary of the district with a 1:50,000 scale map. I was proud of all of those accomplishments and even found some gemstones in the district: native gold (of course), and a few fabulous aquamarine gemstones in the Louis Lake pegmatites along the western edge of the greenstone belt. One of these, a good friend of mine and part owner of the Duncan mine, dug out from a solid pegmatite over a weekend, using an old method known as single jacking he learn years ago working in a mine. Good thing he dug it out, if it would have been me, it would have been in 10,000 pieces - but Elmer got it out in two pieces!

Then, I had another project, another, and another. I mapped the Seminoe Mountains greenstone belt north of Sinclair Wyoming, searching for gold and gemstones. The project was very positive - and at the end, I published several more papers on the area, stepped on a rattlesnake, learned I could jump 10 feet high without a pole-vault, and found some lapidary material in the banded iron formation, some fuchsitic quartzite, cuprite, malachite, chrysocolla, visible gold specimens at the Penn mines. Likely, the two most valuable discoveries were the occurrence of a potentially giant, Tertiary to Recent gold and pyrope garnet paleoplacer along the northern flank of the Seminoe Mountains. Actually, I did not discover gold in the paleoplacer. This was made by two wonderful people - Donna and Charlie Kortes! Yes, the Kortes Dam and everything else out there with the Kortes namesake, is named after Charlie and his family tree.

I still remember meeting them at the Sunday Morning mine. They wired together a couple of step ladders and lowered me into the mine. While I was exploring the extension of the mine tunnel, the thought occurred to me - "Hey, I don't even know these two. They could easily pull out the ladder and no one would find me for weeks". But, these two were absolutely wonderful, and they did let me out of the tunnel. Thank God!

Anyway, Charlie and Donna took me out near the Miracle Mile on the North Platte River which I wrote about in one of my Gemstone Books. We started dry panning some of the dirt from the paleoplacer and finished panning at the North Platte - it all contained a few colors. While panning, I was more impressed by all of the pyrope garnets I found. Later, I was able to get some of the garnets tested for chemistry, first at a lab in Russia due to my co-author (Dr. Ed Erlich) on a diamond book we wrote who had connections in Russia. Later, we also tested other pyrope garnets at the UW microprobe laboratory - every garnet tested (not many as I didn't have any budget to speak of), tested out to have the right combination of magnesium and chromian enrichment comparable to diamond inclusion garnets indicating that somewhere in that region, there are some diamond deposits to be found! So, when you are out in this paleoplacer searching for gold, there is a good chance you may pan out diamonds.

After finding significant gold in the Rattlesnake
Hills, I published the above book and several other
Anyway, I next went on to map the Rattlesnake Hills greenstone belt where I had found evidence of gold at several places. And if the state would have provided me with a reasonable budget, I guarantee I would still be finding gold in that region. In addition to gold, I identified a jasper-jasperoid deposit that has fossil leaf imprints. After I finished reconnaissance mapping and exploring of the Rattlesnake Hills, I published several more papers on the geology and mineralization of that district.

So, how did I find so many gold deposits in the Seminoe, South Pass, Rattlesnake Hills greenstone belts and other mining districts in Wyoming? It was easy. I found hundreds of gold anomalies by using the following prospecting. I went to places that had already been mined and prospected (with the exception of the Rattlesnake Hills - for some reason, it remained an unknown commodity, but the geology was super! A greenstone belt with rocks enriched in gold, and several alkalic volcanoes that intruded the greenstone belt providing heat engines and breccias to mobilize and concentrate the gold).

Well, now you know why I don't smile for cameras - my old
office with dozens of awards for my accomplishments. 
The old prospectors found a lot of gold deposits in the 19th century. But, they only mined what they could find that was minable at a profit when gold prices were only $20.67 per ounce. Last I looked, the gold price was just under $1,300 per ounce. Because of the high gold prices of today, we can mine a lot of material that the old timers ignored and threw away. So, if you want to find a gold deposit, examine old gold districts, figure out the controlling structure(s) (where do all of the old mine dumps, head frames and prospect pits line up), and start walking along that structure. In between each pair of mines and prospect pits, the same gold structure is still under your feet, maybe just below a few inches of dirt, but its there. But also keep an eye out for low-grade gold. At the Carissa mine at South Pass, I found evidence of a giant gold deposit - a shear zone that was as much as 1,000 feet wide and more than 1,000 feet long, with a minimum depth of 970 feet deep and likely continues a thousand feet or more at depth. That is a lot of gold! And then, how much more gold has been missed from the Carissa to the Duncan and the Tabor Grand mines?  Wow, there is a real gold mine out there! Now, look at these gold structures and where are they cut by streams and gullies - yep, there are gold placers down slope and stream from these. Now this is a simple prospecting method.

Putting together the final touches on my South Pass
geological map.
But these were not the only ones. I have to laugh at this next one because it is soooooo simple. After I found gem-quality iolite at Palmer Canyon, it occurred in association with other gemstones including ruby, sapphire and kyanite. The close association of the corundum minerals with a rock type known as vermiculite schist led me to five new ruby discoveries almost over-night. Arthur Hagner wrote a book on vermiculite in Wyoming in 1944. I had a copy, so I read through it and after a short time it was clear to me that the aluminum-rich vermiculite was an alteration product related to relatively high-grade metamorphism and such deposits will have aluminum-rich minerals - and hopefully some of those aluminum-rich minerals will have good color and clarity and yield gemstones. Corundum (ruby and sapphire) is aluminum oxide. Some other minerals such as kyanite, cordierite (iolite), andalusite, sillimanite and staurolite are all aluminum-rich silicates created at high metamorphic pressures and temperatures. So, all I had to do was to take Hagner's book and visit all of the vermiculite deposits I could in Wyoming. I couldn't get access to all, but five yielded rubies. For those of you who would like to find a ruby deposit for yourself, try doing the same in Montana and you will likely find some ruby deposits.

Me today


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  4. Thank you for all of your hard work. I know you had a great deal of fun doing it and Im quite sure your name and the publications you have produced will remain for generations to come. Its a privilege to have read your blogs and possess many of your publications. It would have been a dream come true for me to have worked with you on your projects... Im hoping someday soon I can accumulate enough resources to hit wyoming and prospect.. I have faith that your educating efforts will help make that a success

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