DIAMONDS, DIAMONDS & MORE DIAMONDS

Gem diamonds from Kelsey Lake Colorado.

My first experience in diamond hunting occurred back when I mapped the Wyoming State Line kimberlite district. I  later mapped the Iron Mountain and Sheep Rock kimberlite districts and the Leucite Hills lamproite field. And when I had time, I  explored for diamonds as a consultant for US, Australian, and some Canadian companies. 

I searched for kimberlite, lamproite and lamprophrye in California, Kansas, Montana & Wyoming & identified, a few hundred cryptovolcanic structures within & surrounding the State Line in Colorado and Wyoming - some of which are likely diamond deposits (nearly all remain unexplored)! A few  include Indian Guide, Twin Mountain, Happy Jack & others. I expanded my research & found cyptovolcanic structures in Canada & even in the Kimberley region of South Africa, and found a major anomaly of 50+ anomalies sitting along Interstate-80 in Wyoming!

16.8 faceted gem diamond, Kelsey Lake, Colorado

Diamond deposits south of Laramie are in kimberlite pipes & placers. The kimberlites are deeply eroded & spilled millions of diamonds into the surrounding streams, but no one ever systematically looked for diamond in the creeks (even so, diamonds were accidentally recovered in Rabbit Creek along with a 5-carat diamond, and hundreds were recovered in George Creek, and several including a 6.2 carat diamond were recovered in Fish Creek, but the rest of the streams are mostly UNPROSPECTED!

Kimberlite is a ultrabasic, potassic igneous rock that erupts along fractures from 90- to 120-mi depths. They typically occur in very old cratons & cratonized rocks (basically ancient continental cores that consist of >1.5 billion year old granite, gneiss & schist). The magma, under pressure rises rapidly from the mantle because of the great depth & because of considerable water vapor & carbon dioxide under pressure. Some suggest gaseous emplacement velocities of kimberlite are on the order of Mach 3. The eruption is relatively cool: CO2 gas expands cooling the magma such that emplacement temperatures of 32 degree F are not uncommon. This collection of unusual characteristics results in small, circular maar-like volcanoes (without cones) & dikes that are structurally controlled.

Gem diamond with excellent characteristic
trigons on surface

Things to keep in mind: kimberlite will serpentinize because of water vapor, this produces a relatively soft rock that erodes faster than surrounding country rocks & usually results in a depression with different vegetation than the surrounding rocks. These depressions may contain shallow ponds. They are structurally-controlled such that >one anomaly is often found in a line. Because of calcium carbonate in kimberlite, carbonate will leach out into the pond staining the soil white. Keep in mind that salts are not all that uncommon in basins where lots of young sedimentary rocks occur with considerable carbonate. But in the craton basement (i.e., mountain ranges of Wyoming) there is no known source for carbonate, so if you spot a structurally-controlled lake surrounded by salt in old Precambrian rock, you might want to find out why? When you find one, typically, you will find others along the same structure.

Diamonds found in Colorado & Wyoming ranged from microdiamonds to 28.3-cts & included one chip from a 80- to 90-carat stone. Many people erroneously assume there are no commercial diamond deposits in this region - but all four diamond mills that were constructed in the district, were so poorly designed that they likely rejected as many diamonds as they recovered. Even so, commercial diamond deposits were encountered at Kelsey Lake and mined for only about 6-months before lawsuits shut down the operation. Thus, only the very top of the diamond pipe was touched by mining and thousands (if not many millions) of gem-quality diamonds lie in the host kimberlite and remain unmined!  And this doesn't even include the thousands of placer diamonds eroded from the kimberlite and carried downstream over geological time. 

A flawless, 14.2-carat octahedral diamond recovered from
the Kelsey Lake diamond mine. Photo courtesy of Howard
Coopersmith.

Then there is the Sloan 1 and 2 kimberlites in Colorado. DiamonEx from Australia was developing this property for commercial tests when the economy crashed in 2008 and put most diamond operations out of business including DiamonEx Ltd. Up to that point, the property appeared to be commercial based on the diamond ore grades.

All of the mills in the State Line district were so poorly designed they rejected diamonds of all sizes. The Kelsey Lake mill rejected anything weighing >40 cts! It also rejected many diamonds under 40-cts such that when the tailings were tested in 1997, the first sample yielded a 6.2-ct gemstone along with other diamonds!

High wall of Kelsey Lake kimberlite, State Line district, Colorado-Wyoming. Nearly all of the 
diamondiferous kimberlite was abandoned and never mined because of lawsuits. To this day (2022) 
this diamond deposit remains mostly unmined.

The grades of several kimberlites were high, the gem:industrial ratios were good & diamond values were reasonable. The biggest problem with the State Line district was that diamond mill expertise was in short supply.

CAPE RUBIES, CAPE EMERALDS, GARNETS

Diamonds were discovered in Wyoming & Colorado in 1975 by Mac McCallum, Chuck Mabarak & the USGS. This lead to some exploration for diamonds. Associated with diamonds are a host of extremely rare mantle nodules & gemstones known as Cape Ruby (pyrope garnet), Cape Emerald (chromian diopside & enstatite) that are always overlooked by mining companies. Yet these are very attractive, value-added gemstones. With some marketing skills, could potentially capture large parts of the colored gemstone market. For example, many Cape Emeralds are much more saturated & beautiful than emerald.

These gems were found by many prospectors and geologists all over Wyoming & northern Colorado. Large areas in the Green River & Bighorn Basin contain these diamond indicator minerals, yet little exploration has ever occurred for these or their source rocks.

Photos - Diamond indicator minerals from Sloan kimberlite, Colorado, & faceted pyropes from Green River Basin, Wyoming & Kyanite Eclogite from the Aultman 2 kimberlite, Wyoming.

GOLD & OTHER PRECIOUS METALS

Mineralized terrains of Wyoming (after Hausel and Hausel, 2011).

Little was known about gold in Wyoming when I began research on the geology and mineral deposits of the Cowboy State; thus, I set out to map, evaluate, & find more gold, and it almost seems like I discovered gold nearly everywhere I looked. I was amazed at how much had been overlooked - me and my small team even found anomalous gold in a paleo-drainage in the Laramie City landfill! I published a few compendiums for prospectors & geologists, & mapped several mining districts that were previously unmapped or only partially mapped. I even found a previously unrecognized ultramafic massif with significant palladium, nickel gold & copper mineralization & a whole new district.

34-ounce nugget recovered from the Rock Creek placer, South
Pass district, Wyoming.

There are many great stories & memories about discoveries & prospectors I met. Hopefully, I will be able to find time to write a book about these, as such stories should be preserved. There are stories about hundreds of nuggets in ball jars in Shorty Haddenham's trailer at Atlantic City, dozens of nuggets found by a Ft. Collins prospector, a prospector who spent one entire winter jumping a claim & panning out barrels of mica thinking he had found the Mother Lode & my research along the UP corridor- we found gold everywhere including the Laramie City dump.

I mapped the South Pass greenstone belt at the southern tip of the Wind River Mountains which included several historic gold districts: Lewiston, South Pass, Atlantic City, Miners Delight & others. I identified several hundred gold anomalies & found gold was structurally controlled in reef ore shoots that are very rich down plunge. One deposit I mapped (Carissa) is a major deposit 1000 ft wide, 1200 ft long & probably continuous a few thousand feet downdip. This deposit was withdrawn by the legislature without any scientific review - such abuse of political power literally took away a mountain of gold & many good jobs.

Geology led me to many discoveries. The Rattlesnake Hills were an obvious target, so in 1981, armed with the concept that the RH were part of a fractured greenstone belt intruded by Tertiary alkalic volcanic rocks, I knew there had to be gold. And I found gold in the Rattlesnake Hills in veins, shears, Tertiary breccia, stockworks, pyrite. I also found significant gold elsewhere in Wyoming - Seminoe Mountains, Mineral Hill, Purgatory Gulch, more.

OTHER GEMS

Blue barite from the Mine Hills near Shirley Basin, Wyoming

While conducting field research over 3 decades while at the Wyoming Geological Survey at the University of Wyoming, we were able to document hundreds of mineral deposits, occurrences and anomalies. We were able to do so by using scientific methods by keeping in mind the geology, tectonics, and geological history. Sure, we found a lot of stuff, but I guarantee you, if you apply similar scientific methods, you will also find a many more mineral deposits in Wyoming - the geology along with mineral anomalies we identified, prove that there are many other deposits including several ruby and sapphire deposits, more iolite deposits, many diamond deposits, dozens of gold deposits, many massive sulfide deposits, etc. 

While conducting reconnaissance, jasper cobbles and boulders were found in several old prospects at Tin Cup, in an outcrop near the south edge of the Rattlesnake Hills, and (jasperoid) at Quaking Asp Mountain. Some of the Tin Cup jasper is extraordinary and found in masses weighing several hundred pounds. The jasper in the Rattlesnake Hills contained some fossil leaf imprints.

Nearly everywhere we explored, we followed trends and examined geology which lead to other mineral deposits. I was curious enough to find out what some of the unusual minerals were that I picked up, and as a result, identified more than a dozen minerals that had never been reported in Wyoming.

OPAL

Resistant, opal, boulder adjacent to rock hammer in Tertiary
volcaniclastics, with a seam of resistant opal lying beneath the
 boulder and hammer, Cedar Rim, Wyoming.

A rockhound from Riverton, Wyoming, mentioned opal was reported south of town near Cedar Rim at one of my rock hound club talks. When I returned to Laramie, I began searching old US Geological Survey reports on the stratigraphy of the area and found, in passing, mention of opalized rock in some of the stratigraphic columns - so, I headed to the area not knowing what I might find, but the reports left me with the impression that these were just trace amounts. So, when I arrived at Cedar Rim, I was absolutely amazed at the extent of the opal. The great majority of the material I classified as common opal, but also found an entire hillside with colorful red-orange, orange to yellow Mexican opal, and Mexican opal breccia, and traces of precious opal, along with dendritic agate (Sweetwater agate) and a host of colored agates. Based on the presence of the precious opal, I suspect some seams might be found at depth. After spending a few days in the opal field, I later found additional US Geological Survey reports describing some opalized tuffaceous sediments located to the west and east of Highway 135 suggesting that there is likely more opal to the west of the Cedar Rim deposit.

Specimen of 'Candy' opal from Cedar Rim - a mix of white
common opal with colored 'Mexican' opal.

The Cedar Rim deposit lies east of highway 135 and is cut by oil field roads. A few old geological reports from 50 t0 80 years ago mention opal in passing, so I was surprised to find opal scattered over 14 mi2, opal masses containing 80,000-carats along the edge of the oil field roads, and common, fire & precious opal and scattered Sweetwater agate, along with some of the nicest decorative stone in Wyoming. All occurring in Tertiary-age volcaniclastic sedimentary rocks that had a notable

contribution of volcanic ash erupted from Yellowstone in the past.

Cedar Rim boulder opal. All of the boulders and
cobbles that stand out as resistant rock, is typically
filled with opal.

This gave me a clue - nearly all of Wyoming was blanketed by volcanic ash (as was Nebraska and South Dakota). Guess what? There are other opal fields waiting to be discovered. So I found millions of carats of common & fire opal & traces of precious opal (including black opal) that suggest as soon as someone digs, valuable veins of precious opal will be found as depth!

The waxy material in the rock matrix is common opal. 

IOLITE (WATER SAPPHIRE)

A flawless iolite gemstone

What the heck is iolite? Geologists typically describe this mineral as cordierite, while gemologists typically refer to it as iolite or water sapphire. Guys don't have a clue to what this beautiful mineral is, but many women either have a ring with some iolite, or they've seen in on TV. It is every bit as attractive as Tanzanite, but at about 1/10th to 1/20th the price. Why? Because Tazanite was marketed by a retail gemstone company, and iolite has not been marketed.

I discovered iolite (water sapphire) at Palmer Canyon in 1995. The iolite occurred with gem-quality kyanite in mica schist & gneiss adjacent to vermiculite that had enough silica to form these gems. I couldn't believe the amount, size & beauty of the stones. The single, largest, iolite gemstone on earth was found at this time -the baseball sized Palmer Canyon Blue Star- a 1,720 ct flawless gem.

First group of iolites gems cut from
Palmer Canyon rough. The bed of
material that the iolites sit in has tiny
white fibers that unfortunately sit
in front of the iolites at the top. But
these iolites were flawless.

So I went looking in similar terrains & predicted in a book I would find iolite at Grizzly Creek to the south. In 2005, I discovered iolite at Grizzly Creek & recovered the largest iolite gem (24,150 carats) on earth (the football sized Grizzly Creek Blue Giant), but this was dwarfed by giant, VW bug-sized masses in the outcrop I left behind because I didn't have tools necessary to recover such large gems of 1 to 5 million + carats. Based on geology, I predicted several other iolite deposits would be found in central Laramie Range & Copper Mountain, but most remain unexplored. Over the years I tried to get some investors interested in forming a company to take advantage of these giant deposits - explore for more, mine them, cut the gems, design jewelry and market them, but no one wanted to take on this task, so they all essentially sit there collecting dust and eroding away.

But nothing could match the potential discovery further to the south. Some geologists had

explored this region for aluminum & magnesium & during the mid 20th century and they reported one deposit that had been trenched and mapped contained 500,000 tons of cordierite (when gem-quality, cordierite is known as iolite). I began looking at this deposit & found flawless gem-quality ioilte along the edge of the deposit. All of the material reported by theses earlier geologists likely was part of the largest gemstone deposit found in history. But they were so focused on the use of the material for magnesium and aluminum, they overlooked the gem potential. Besides, in the mid-20th century, there was not much of a market for iolite gemstones.

Iolite in outcrop at Grizzly Creek, Wyoming. Note the rusty matrix to the
right of the iolite. This is limonite replacing the iolite. Iolite has considerable
iron and will 'rust' under the right conditions.

But let's look at this deposit as a potential gem deposit. It is unexplored for gems except along the one margin where everything I examined was of the highest quality gem material. The rest of this deposit needs to be examined. Why?  One ton of material contains 4.5 million carats! Multiply that by 500,000 tons and this could potentially have more than 2 trillion carats just on the surface and no one knows how deep it goes. If it is just 100 feet deep (it likely is a few thousand or more feet deep), it would dramatically increase the amount of recoverable gemstones. Iolite sells for only about $15 to $150 per carat, but if marketed like Tanzanite was marketed, one could increase the value of this (and other deposits in this region) to the most valuable mineral deposits on earth! But to develop this will take a lot of money and support.

The Palmer Canyon blue Giant sits on cover of
ICMJ Prospecting & Mining Journal. At 1,750
carats, this was the largest iolite gem reported
in the literature until I found much larger
stones at Grizzly Creek, Wyoming.

So what did I get for finding two of the largest colored gemstone deposits on earth? Well, like the song goes, the director got the mine and I got the shaft. But am I bitter? Yes!

Largest iolite in world at 24,150 carats from Grizzly Creek, Wyoming. Much larger stones were left in outcrop.

PERIDOT

In 1997, I decided to search the Leucite Hills in western Wyoming for diamonds (see photo at left). I didn't find diamonds, but mark my words - "DIAMONDS WILL BE FOUND HERE". This is an easy prediction to make based on geology.

The Leucite Hills consist of several lamproite volcanoes & flows that erupted 900,000 to 3.1 million years ago. They started their journey under one of the thickest parts of the Wyoming Craton. Cratons are very old, cool, continental cores necessary to have melting deep within the earth's upper mantle (where diamonds are formed). While exploring this region, I collected grab samples from lamproite in the northeastern part of the field & two yielded chromites with similar geochemistry to chromites found as mineral inclusions in diamond - thus this tells me some of the volcanoes began their journey at 90 to 120 miles beneath the surface where diamonds are common.

Diamondiferous lamproites are found at Murfreesburo, Arkansas; Argyle & Ellendale, Australia; Majhgwan-Chelima, India; Kapamba, Zambia; Aldan, Russia & Bobi, Ivory Coast. The richest deposits are typically found in olivine lamproites which often alter to serpentinite (a very soft material) that erodes quickly, thus such deposits are usually hidden within a field of leucite lamproites (which are much harder rock). Thus, this all suggests a few diamonds are likely to occur in the lamproites with diamond-stability chromites, but the locations for rich diamond deposits are hidden. Along the northern edge of this field, a large sand dune field that marks the location of a major continental shear - a favorable structure for hidden lamproites. One can almost guarantee there are diamondiferous olivine lamproites in this area hidden under a few feet of sand. Lamproites are also well known for colored stones - brown, yellow & the beautiful, extremely rare Argyle 'Pinks'. Some have sold for >$US1 million/carat!

While searching for diamonds, I started looking for olivine. In 1997, I came across two green anthills at Black Rock - the ants had collected all of the available olivine in the immediate area & decorated their hills. So I collected the hills & processed them for diamonds - but all we found were 13,000 carats of flawless peridot (gem-quality olivine). Some were 12 millimeters in length. I also found peridot in place that were nearly 0.5 inch across.
Even though olivine had been recognized in this area >100 years ago, no one had ever looked at the quality of the olivine. Later, I mapped the Leucite Hills and identified all of the olivine bearing volcanoes.

GEMSTONES & GEOLOGY

A good understanding of geology, persistence, & luck can lead to incredible treasures. In 1977, I started work as a research geologist at the Wyoming Geological Survey in Laramie. Next to nothing was known about gemstones in the state, but over the years, I tracked down many mineral deposits & found some of the largest gemstone deposits ever found on earth. Anyone can do it. 

My story is found in many publications and blogspots, the most recent available at Amazon, the Wyoming Geological Survey publications office and the University of Wyoming bookstore in Laramie, as well as at your local bookstore.

Some of the many gemstones discovered in Wyoming since 1977.