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.

Found more gemstone deposits and previously unknown minerals in Wyoming than any other person. More than anyone should have been able to do. After developing some good prospecting models for finding gold and gemstone deposits - I went searching for more mineral deposits. 

Gemstones have unique qualities that make them attractive. If they are translucent to transparent, or have bright colors or color combinations, they could potentially be used in jewelry. Others just have unique shapes that make them attractive, such as some staurolite or cordierite (iolite) specimens. Sounds simple, but gemstones were almost completely ignored in Wyoming prior to 1977, and because some geologists stated that there were none (other than jade),  people believed them. But, I wasn't so sure, and after I began searching, I even found gemstones adjacent to highways and 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, students are not taught to look for gems - it's that simple. And instead of calling peridot "peridot", geologists call it "olivine". Instead of calling iolite "iolite", we are taught to call it "cordierite".

Then there are gemologists - they can recognize gems, but most 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? Not yet.

One of many tpublications
by the author

Take for instance the discovery of gem-quality peridot in Wyoming. Some years ago, while searching the Leucite Hills near Rock Springs for evidence of near-surface, buried, olivine-rich lamproite 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. Nope, didn't find any diamonds associated with those lamproites, but did find some diamond-indicator minerals with good chemistry that suggest a diamond or two might be found in the Leucite Hills, while searching, I recovered over 1,300-carats of gem-quality peridot! Some famous geologists from the past looked at those same olivine crystals and saw nothing much of interest. I looked at them, and I saw gemstones!

In 1986, the Wyoming Geological Survey had a competent director who requested a special appropriation from the legislature to send me to Western Australia to study the newly discovered diamond pipes for about a month. Three things I brought back from Australia with me - (1) they have jack rabbits that are much taller than the Wyoming rabbits and the Aussie jack rabbits also have pockets, (2) the people speak funny, (3) and the newly discovered diamond deposits occurred in olivine lamproite - not kimberlite. And guess who had the largest lamproite field in North America? That's right - Wyoming! So, I had another project for 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
a 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. 

In 1991, I finished the South Pass greenstone belt, published numerous papers, eight 7.5 minute quadrangles with geology, wore out a few pairs of field boots, tipped several beers with 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 those accomplishments and even found some gemstones in the district: native gold (of course), helidor beryl (which led a prospector from Lander, by the name of Elmer Winters, Jr., to find a fabulous aquamarine gemstone in the Louis Lake pegmatites along the western edge of the greenstone belt). Elmer (RIP), was a good friend of mine and part owner of the Duncan mine. He dug on a solid pegmatite over one weekend using an old method known as single jacking from 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 papers on the area, stepped on a rattlesnake, learned I could jump 10 feet high without a pole-vault, and found 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, but, if it wasn't for that mapping project, I would never have met the Kortes's, and we would most likely not know about that paleoplacer.

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 a Gemstone Book. 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 at a lab in Russia due to my connection with a co-author (Dr. Ed Erlich) on a diamond book we wrote. Later, we tested other pyrope garnets at the UW microprobe lab - and every garnet tested (not many as I didn't have any budget to speak of), tested to have a favorable combination of magnesium and chromian enrichment comparable to diamond inclusion garnets, that indicate somewhere in that region, there are some diamond deposits! 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 and found evidence of gold. In addition to gold, there was a jasperoid deposit with some uncommon 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 method. I went to places that had already been prospected! Then I lined up the prospect pits on aerial photos, and looked for evidence for additional mineralization, such as vegetation anomalies, quartz outcroppings, narrow resistant ridges (indicating silicification, i.e., veins), lineaments, and gossans. And I went searching the Rattlesnake Hills primarily because it was a greenstone belt with rocks enriched in gold, with several alkalic volcanoes that intruded the greenstone belt, providing heat engines and breccias necessary to mobilize gold from the rocks and concentrate the gold.

A 1.1-carat, ruby, from Palmer Canyon
Wyoming. Photo courtesy of Chuck
Mabarak.

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.

A 1.4-carat iolite from Palmer
Canyon. Photo courtesy of Chuck
Mabarak

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.

The author in Arizona.

Job 28:16

Recognizing Ruby and Sapphire in Nature

Low-quality corundum (variety - ruby) in a schist from the Wind River Mountains, Wyoming
(found by Dr. Ron Frost). Many prospectors would misidentify these as garnet, but look close, and
you will see distinct, parallel cleavage in the largest ruby - 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 gems: so a gem prospector must learn to recognize the natural, physical, characteristics of this gem to identify raw material in the field. And a prospector also needs to learn where to look in the field, and how to identify possible host rocks.

Some time ago, I received a 25-year longevity pin from the State of Wyoming for my service to the State. It was a tiny, plastic pin about the size of nickel that had a tiny, red, ruby. So, I took this spectacular gem to my lab to examine with a binocular microscope, and it was obvious that it was a synthetic ruby almost too tiny to weigh. The ruby may be worth about $1.00 and and the pin another $1.00 (pre-Biden prices). No idea where it was made, but my guess is China. If the state government had any creativity, one would think they would search for a good, Wyoming rock hound to dig some  Wyoming rubies (and other gems), facet them, and make them into longevity and dedication pins for their employees. As such, Wyoming would actually contribute to the state's economy and also provide a great means of advertising for the state's natural resources. Employees would be proud, particularly after they learned a little information about the history and gemology of the gems! 

When it comes to learning to identify minerals, there are flaws with most gemstone and mineralogy books - they are not designed for prospectors or rock hounds. Essentially, all books show spectacular, faceted, gems or museum-quality mineral specimens that are rare. 

Corundum in schist cut perpendicular to prism, showing 
distinct outline of hexagonal crystal habit. Sample from Wind
River Mountains collected by Dr. Ron Frost. Locality could
not be verified.

Hexagonal, prismatic corundum (pink sapphire) in vermiculite
schist, collected from Palmer Canyon, Wyoming. Yellow arrows
point to numerous crystals of pink corundum.

The two photos above show the characteristic crystal habit of corundum (geologists' term for ruby and sapphire). The upper photo shows a cross-section of ruby in schist with a characteristic hexagonal (6-sided) crystal habit, while the lower photo shows another corundum (pink sapphire) with its crystal habit perpendicular to crystal in the upper photo. This lower mineral is still hexagonal, but now we are viewing the long, crystal axis, which shows what geologists call a prism (or prismatic crystal habit). One mineral that is sometimes mistaken for ruby or sapphire, is garnet. But don't feel bad as I've known geologists who make that same mistake.

Ruby and sapphire exhibit atomic flaws known as crystal parting: linear, structural (atomic) planes in a crystal. This are actual planes in a mineral that gemologists might to break a mineral, or avoid when cutting the mineral, because they are a zone of weakness in the crystal. These are useful in identifying minerals like corundum (ruby, sapphire) and they do not appear in garnet. Few people are familiar with the term 'parting', but it is similar to mineral "cleavage". Corundum (sapphire and ruby) typically exhibits three directions of parting.

Pink sapphire from Palmer Canyon, Wyoming showing distinct plane cutting through the edge of
the gem. This is what is known as a parting plane. Most mineralogists describe corundum as having
three parting planes, while a few report the presence of at least one cleavage. However, cleavage
appears to be absent in corundum.

A 12-carat ruby collected in Palmer Canyon, Wyoming held by tweezer. Note the parallel lines
(twin planes) in the side of the crystal.

Beautiful pink sapphire from Wyoming. The stone is flawed by numerous intersecting (parting
planes.

Possibly, the largest ruby on earth (prior to alteration to the green zoisite! Yes, this was once all
 ruby, prior to changing physical conditions in the geological past that resulted in much of the
 former ruby being replaced by another mineral.  When the ruby formed, the entire specimen was
one, very-large, ruby. But it became unstable at depth in the earth's crust and reacted with
metamorphic fluids until much of the ruby was replaced by more stable zoisite. Imagine wearing a
ruby this size in necklace. The base of the ruby was cut by a diamond-bladed rock saw.  Even
 though the ruby was flawed, it provides us with a example of what may lie deeper at depth. 

This Oriental Amethyst (its not amethyst
but jewellers use this term for violet-colored
sapphires) will produce twinned crystals attached
to one another.

A beautiful ruby flawed with rhombohedral
parting. Even so, it makes a great gemstone. 
Most are translucent like this one recovered south of
Encampment Wyoming.

 These rubies were found by my son Eric Hausel and show nodular texture.

Pink to violet sapphire prism (left) with a purple-red (pigeon's blood red) ruby in rock
  (right). The ruby is enclosed by green zoisite reaction rim.

Ruby from Granite Mountains, Wyoming. Note the rubies are enclosed by green zoisite reaction rim. 
The zoisite reaction rim and ruby form a porphyroblast within the host rock - fuchsite schist.

Twinned Oriental Amethyst (oriental amethyst is an archaic term for lavender-colored corundum.

 

Pitted gem sapphire from Montana with rounded crystal faces.
This sapphire was collected from placer and the rounded crystal
faces are due to erosion and stream transportation.

Serpentinite with 15 to 20%, light-blue,  equigranular, sapphire discovered in the Granite Mountains
Wyoming by Robert Odell.

Sapphire schist from Palmer Canyon. 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.

RUBY & SAPPHIRE IN WYOMING

Faceted (transparent red) and cabochon (opaque cab) rubies sitting on specimen of corundum
vermiculite schist collected in Palmer Canyon (photo by the author. Gems weigh a little more
than 1-carat each.

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.

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 parting (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 often referred to as metapelite, mica schist and hornfels.



Ruby with parting 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.

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.

Large ruby-zoisite porphyroblast from Red Dwarf deposit found by J. David Love of the US Geological Survey. Much of this giant ruby was replaced by zoisite, but 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 suggests that large rubies remain to be found at the Red Dwarf.

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.

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. 

Beautiful specimen of reddish-purple corundum (variety - ruby) collected by Eric Hausel from the
Red Dwarf deposit, Granite Mountains, Wyoming (photo by Robert Odell).

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.

Palmer Canyon corundum schist showing some pink corundum (var. sapphire) enclosed within blue
kyanite in the vermiculite schist (photo by the author).

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.

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) indicating the presence of ruby deposit. According to Dr. Frost, this ruby deposit is widespread within the southern core of the Wind River Mountains. Location, however, could not be verified and may be erroneous.

 

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.