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
papers.

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

Job 28:16

Ruby, Sapphire, Kyanite, Sillimanite and Iolite at Palmer Canyon Wyoming

After I discovered iolite at Palmer Canyon, I made more discoveries as well as a half-dozen ruby deposits and a couple of kyanite gemstone deposits. I was amazed by how many gemstones, diamond, and gold deposits that had been overlooked in Wyoming: I can guarantee using the exploration models I developed for these deposits, I would have found dozens (if not hundreds) more gem and gold deposits. But it was time to move on and I took early retirement.

But there are still some more gemstone deposits to find that I didn't get time to search for. As you think about rubies and sapphires - keep two rock types in mind while prospecting in Montana, Wyoming Colorado, and California - vermiculite and serpentinite!  These are very good host rocks for these gemstones. To find out more about these, I summarized the characteristics of ruby, sapphire and their host rocks in a couple of recent books.

Kyanite-ruby-vermiculite schist, Palmer Canyon, west of Wheatland, Wyoming.

A more than 18,000-carat iolite boulder of ioite. The iolite is partially altered to limonite and the boulder includes
milky quartz. Palmer Canyon, Wyoming.

Specimens of vermiculite schist filled with purple-red ruby, Palmer Canyon.

Iolite in schist, Palmer Canyon, Wyoming

Excellent iolite (more than a thousand carats) from an undisclosed Wyoming locality

Kyanite schist, West Cooney Hills, Wyoming

Beautiful iolite rough in gneiss from undisclosed locality, Wyoming

Ruby in vermiculite schist from Palmer Canyon

Recognizing Ruby and Sapphire in Nature

Several rubies in a schist from the Wind River Mountains, Wyoming. Most prospectors would misidentify these as rubies,
but if you look close, you will see distinct, parallel cleavage in one of the rubies - something that does not occur in garnet.

Best of Show - Rubies, sapphires, and iolite gemstones found in Wyoming and faceted in Sri Lanka.

When you think of ruby and sapphire, you probably think of spectacular, faceted, over-priced gems in rings and necklaces. Unfortunately, Mother Nature does not facet her gems: so the gem prospector must learn to recognize the natural, physical characteristics of this gemstone to identify the raw material in the field. The prospector must also learn where to look in the field.

I remember receiving a 25-year pin from the State of Wyoming for my service in finding several hundred $million in gemstones, gold and diamonds for the State. It was a tiny plastic pin about the size of nickel that had a tiny red ruby. After examining this valuable ruby with a microscope, it was obvious it was a synthetic ruby almost too small to weigh. The ruby was likely worth about $1.00 and and the pin another $1.00. Have no idea where it was made, but I would guess China. Why thank you Wyoming for thinking about me.

When it comes to learning how to identify minerals, there are serious flaws with most gemstone books - they are not designed for the prospector. Essentially all show spectacular faceted gems or museum quality specimens that you are unlikely to find in nature. I'm too poor to afford cut gems, so I have to find my own in the rock. So, here are some hints of where to look and what to look for.

The two photos above show the characteristic outline of corundum (the geologists term for ruby and sapphire). The upper photo is a cross-section of ruby in schist showing the characteristic hexagonal (6-sided) cross-section and the lower photo shows another corundum (pink sapphire) at an angle perpendicular to the upper photo. The mineral is still hexagonal, but now we are viewing the long axis which shows what geologists call a prism.

One of the few minerals that you might mistaken for ruby or sapphire is garnet. But don't feel bad as I've known geologists who make this mistake.

Ruby and sapphire also have atomic flaws known as parting where we can see these atomic planes in the crystals and these surfaces also provide locations for twinning of crystals. This are actual planes in the mineral that many gemologists use to break the mineral, or avoid when they cut the mineral. These are useful in identifying the mineral because they do not occur in garnet. But few people are familiar with the term 'parting', so for our purpose, we will refer to these parting planes as "Cleavage", and corundum (sapphire and ruby) have three directions of parting ('cleavage').

Here is a very nice sapphire I found in Wyoming, but the gem cutter did a very poor job of avoiding flaws. For a
 geological researcher, this is a very nice specimen as it can be used to show cleavage and show others how one should not
 cut a gemstone. This cleavage is a plane of weakness and should have been avoided. The mineral should also have not
 been cut showing the dark mineral inclusions and it needed to be polished.

Another pink sapphire that I found that shows excellent rhombohedral cleavage in the gem. Note the two intersecting
 planes that are nearly perpendicular to one another.

Beautiful pink sapphire from Wyoming. The stone is flawed with numerous intersecting cleavage (parting) planes that can
 be partially hidden by cutting the stone in a cabochon.

This was likely the largest ruby ever found on earth! And it was found in Wyoming!  It exhibits excellent color but you are
 probably wondering what I'm talking about because you likely only see green zoisite with a little bit of ruby color. When
 this ruby formed, this entire specimen was one, very large, ruby. But it became unstable at deep in the earth's crust and
 reacted with metamorphic fluids until much of the ruby was replaced by the zoisite. Imagine wearing a ruby this size in a
 necklace. The base of the ruby was cut by a diamond-bladed rock saw.  Even though this ruby was flawed, it provides us
 with a general idea of what might be found in this particular deposit at depth. If this is ever mined, one likely will recover
some very large rubies hidden beneath the surface.

Some corundum, such as this Oriental Amethyst (its not amethyst
but jewellers use this term for violet colored sapphires) will
produce twinned crystals attached to one another.

Here is a beautiful ruby that unfortunately is flawed with rhombohedral
cleavage. Even so, it makes a great gemstone. It is very rare to find a ruby
that is not flawed. Most are translucent like this one. I found this ruby south of
Encampment Wyoming.

Would you recognize these as rubies?  These rubies were found by my son Eric Hausel and they show nodular texture.

This photo shows a pink to violet sapphire prism to the left and a purple-red (pigeon's blood red) ruby in the rock to the
 right. The ruby is surrounded by what is known as a reaction rim of green zoisite.

In this photo, I'm holding rubies recovered from the Granite Mountains of Wyoming. Again, note that the rubies are
 enclosed by a reaction rim of green zoisite. This suggests that these rubies were all part of one large ruby at one time and
 part of the gem reacted with metamorphic fluids to produce the zoisite.

Another twinned Oriental Amethyst - you should be able to see that this corundum has two crystal that grew side by side.

 

Large, faceted red ruby from the Palmer Canyon ruby-sapphire-kyanite-iolite deposit in the Laramie Mountains. Note the
 distinct parallel cleavage planes.

Look closely at this pretty little gem sapphire from Montana. It is pitted with
rounded edges unlike a sapphire found in outcrop or in eluvium. This is because
it is a placer sapphire that was transported some distance downstream for the source
beds. Several years ago, I found some of the nicest sapphires and benitoite in a
stream in California. None were pitted which suggested that they originated from a
nearby serpentinite.

See anything interesting in this rock? Well it contains about 15 to 20% sapphire. All those light gray to light blue equigranular crystals are sapphire. Many of Wyoming's mountain ranges were subjected to favorable high pressures and temperatures in the geological past for ruby and sapphire. In places where there was sufficient aluminum and little silica, lots of rubies and sapphires crystallized. I suspect that Wyoming has many dozens of ruby and sapphire deposits that remain undiscovered.

Sapphire schist from Palmer Canyon, Wyoming. Note the abundant white to very light blue hexagonal mineral grains. These are all sapphire and this particular sample has about 10% sapphire.

Some of these gemstones will provide few hints of what they are. This 12-carat pink sapphire has an irregular shape, and is nearly flawless, But if you look closely, you will find at least one very distinct cleavage plane and also hints of rhombohedral cleavage.

Wyoming's Ruby and Sapphire Deposits

Wyoming likely has some of the larger rubies in North America. We found evidence for several ruby and sapphire deposits in a number of localities in the State, but ran into road blocks by the Director of the Wyoming Geological Survey following every major discovery. One must wonder why a political geologist would not want his staff to make mineral discoveries?

A 1.1 carat flawless ruby from Palmer Canyon

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RUBY & SAPPHIRE IN WYOMING

Sapphire vermiculite schist from Palmer Canyon. This sample is formed of an estimated 40% pink sapphire and is just one of dozens of samples collected by the author that had from 20 to 50% corundum (ruby and sapphire) by volume.

CORUNDUM (Al2O3)  Characteristics & Habit. Corundum (H=9) is the second hardest naturally occurring mineral: only diamond is harder. As a result, gemstones made from corundum are durable. Raw corundum occurs as barrel-shaped hexagonal prisms with rough, rounded surfaces often exhibiting distinct parting. Because of good rhombohedral and basal parting corundum prisms often terminate at basal pinicoids & display striations due to repeated twinning.

Corundum exhibits a variety of colors including gray, grayish green, blue, pink, brown, red & purple. Some corundum is used to produce extraordinary gemstones. Ruby is the deep pigeon’s-blood red translucent to transparent variety of corundum with adamantine luster and sapphire includes all other colors.

Hexagonal (6-sided) ruby in mica schist.

It will display a striking adamantine to vitreous luster noticeable in faceted gemstones. High specific gravity (4 to 4.1) is favorable for its concentration in black sand concentrates in streams. During sampling in the central Laramie Range, we recovered tiny rubies and sapphires in several sample concentrates in that region, suggesting that several corundum deposits remain to be discovered.

Palmer Canyon ruby mounted in necklace (photo courtesy of Chuck Mabarak) & showing cleavage (right - note the distinct lines in the gemstone).





THE CORUNDUM GEMSTONES include a variety of colors including:
Red Ruby
Cornflower Blue Sapphire
Colorless Leuco-sapphire
Light bluish-green Oriental Aquamarine
Green Oriental Emerald
Yellow-Green Oriental Chrysolite
Yellow Oriental Topaz
Aurora Red Oriental Hyacinth
Violet Oriental Amethyst

Occurrence. Corundum, a high-pressure aluminum oxide, is found with silica-poor aluminum-rich metamorphic rocks in areas of metapelite. Metapelite is the key to finding many gemstones in Colorado, Montana & Wyoming as discussed in my book (in preparation) The Geology of World Gemstone Deposits. Some discussions on these rocks are found in my new book on GEMSTONES in Wyoming.




Ruby with cleavage from
undisclosed location in WY

Metapelite may contain a variety of alumino-silicate porphyroblasts such as mica, kyanite, sillimanite, andalusite, vermiculite & cordierite. The corundum itself is typically found in vermiculite schist and aluminum-rich serpentinites. Vermiculite schist is considered an alteration product of a former metapelite in which metapelite was desilicated leaving mica-rich rock known as vermiculite schist or glimmerite schist. After noting the close association of vermiculite & ruby, I discovered several more ruby deposits in Wyoming. This was also true of iolite and pelitic schist. Using geology proved to be extremely valuable.

Twinned corundum with
distinct hexagonal cross-section

Small, twinned corundum from Wyoming. Note the 6-sided crystal prism that is bounded by pinacoids (flat surfaces).

Localities. Corundum has been found at a number of places in Wyoming. Wyoming could easily develop a major ruby and sapphire industry along with many other commodities - such as diamond, gold, palladium, rare earths, iolite, labradorite, copper, zinc and silver - but its political regime with the US Forest Service have worked for more than 30 years to withdraw nearly all non-energy mineral resources from public lands - something that should be considered illegal. Over the years, we provided evidence for major and world-class mineral deposits and several companies found significant base metal deposits, only to find government interference at every level.

One interesting locality lies northwest of Jeffrey City, known as the Red Dwarf deposit (sections 13 and 24, T30N, R93W), was investigated by me several years ago. The deposit consists of corundum gneiss & schist with a 5,000 foot strike length with widths of 20 to 50 feet. The rock has 1 to 10% corundum porphyroblasts encased in zoisite-fuchsite reaction rims and considerable fuchsite and zoisite pseudomorphs after corundum. Where found, some of corundum is translucent with good color.

Large ruby-zoisite porphyroblast collected at the Red Dwarf deposit by J. David Love of the US Geological Survey. Much of this giant ruby was replaced by zoisite, but some excellent pigeon’s blood red ruby remains untouched. Prior to replacement, this specimen would have been one of the largest rubies in the world. It also suggests that large rubies remain to be found at the Red Dwarf.

The corundum may be light purplish-pink, lavender, to reddish-purple, and range from millimeter size to more than two inches across. Some gem-quality corundum was found in the past and partially replaced specimens provide evidence for rubies of five inches (or more) in length and more than 2 inches in diameter.

A nearby serpentinite discovered west of the ruby schist contains tiny (millimeter size), light-blue, translucent to opaque corundum. Locally, the serpentinite has 20 to 40% corundum.

Ruby enclosed in reaction rim found by Eric Hausel at Red
Dwarf deposit in Granite Mountains.

At another deposit known as the Abernathy deposit (section 26, T30N, R96W) near Sweetwater Station, pale-blue and white corundum is found in mica schist. The corundum is abundant and occurs as one-inch diameter nodules in the schist.

Corundum is also associated with vermiculite schist (glimmerite) west of Wheatland in Palmer Canyon. This deposit (N/2 Section 18, T24N, R70W) is associated with kyanite, cordierite, and sillimanite schist and gneiss. The corundum forms small, hexagonal, pink, red and white grains from about 0.1 to 0.3 inch across. Many grains have well-developed parting which limits the size of facetable material. Even so, significant percentages have excellent color, and are transparent to translucent (Personal field notes, 1997). Locally, the schist may contain >20% corundum. Small amounts of corundum have also been identified at the Grizzly Creek iolite (cordierite) deposit to the south and other localities to the north.

Gem-quality 8 to 12 carat pink sapphire (left) & sapphire-kyanite schist from Palmer Canyon (right).




Some corundum was identified in vermiculite schist in the Platte River Valley between the Medicine Bow and Sierra Madre Mountains. Another notable corundum locality is in the Big Sandy opening along the southern margin of the Wind River Mountains, where hundreds of corundum crystals weighing up to 90 carats have been collected from Squaw Creek by prospectors (Russ and Joe Sims, personal communication). The source of this corundum remains undiscovered. Some nearby ruby schist float was found (B.F. Frost, Personal communication) suggesting that a potentially significant ruby deposit awaits discovery.

Photos of ruby, sapphire and iolite (blue) gems and raw material from Wyoming. Note the presence of parting (cleavage in some specimens - parallel fractures) and the 6-sided characteristic of the corundum.

Find more information about dozens of rubies and sapphire localities and methods I used to find several of these deposits from my book. See you on the outcrop - the GemHunter.


Below - Raw translucent pink sapphire from Palmer Canyon. Below right -  faceted pink sapphires & blue iolites from Palmer Canyon, & Below far right - large raw ruby from the Rattlesnake Hills, Wyoming. In addition to these stones, the author was following rubies near the Big Sandy opening in the Wind River Mountains, the Rattlesnake Hills, Barlow Gap, the Sierra Madre, the central Laramie Range & the Saratoga valley.