Finding Gemstones

Geology of Gemstone Deposits

2011-10-09T12:14:00.000-07:00

Much of Wyoming is underlain by Archean cratonic basement rocks and cratonized Proterozoic rocks that provide favorable geological environments for a variety of gemstones – notably diamond, iolite, ruby, sapphire, garnet, kyanite, andalusite, sillimanite, labradorite, jewelry grade gold, platinum and palladium nuggets, emerald, aquamarine, helidor, tourmaline, spinel, clinozoisite, zoisite, apatite, jasper, specularite, etc. Thick Phanerozoic sedimentary rock successions with lesser Tertiary volcanic rock cover large portions of the basement terrain. Some of these Phanerozoic rocks provide favorable hosts for other gemstones including opal, placer diamond, placer gold, placer platinum, placer ruby, jasper, agate, emerald, varisite, etc.

Using traditional exploration and prospecting methods, dozens of gem and precious metal deposits were discovered over the past 3 decades, including major discoveries and geological and mineralogical evidence for significant undiscovered deposits. Major swarms of mantle-derived kimberlite, lamproite and lamprophyre, many of which have proven to be diamondiferous, also host colored gemstones including pyrope garnet (Cape Ruby), spessartine garnet, almandine garnet, chromian diopside (Cape Emerald) and chromian enstatite. One lamproite also yielded peridot.

Favorable conditions for crystallization of metamorphogenic gemstones during regional amphibolite-grade metamorphism occurred during the Precambrian. In this terrain, metapelite in the central Laramie Range hosts kyanite, sillimanite and andalusite. These three minerals provide evidence of favorable pressures and temperatures needed for crystallization of aluminous gemstones including ruby, sapphire and kyanite. Cordierite (iolite) another aluminum-rich gemstone, formed during a later thermal event. This later event was responsible for deposition of world-class iolite (Water Sapphire) gemstone deposits.

While searching for gold, came along this giant jasper deposit.

Evidence for undiscovered gemstone deposits is predicted based on mineralogical anomalies detected during various research projects from 1977 until 2005. These include ruby, sapphire, gold and aquamarine found in stream sediment samples as well as favorable geological terrains that remain unexplored. Other anomalies include pyrope garnet (several with G10 geochemistry), picroilmenite, and some chromian diopside that provide evidence for hundreds of undiscovered diamond deposits. Elsewhere, detrital diamonds reported by various prospectors provide direct evidence for undiscovered diamond deposits. Other geological and mineralogical evidence suggest the presence of additional undiscovered opal, cordierite (iolite) and kyanite deposits. Wyoming could potentially become a major source for gemstones including diamond, gold, platinum, palladium, Cape ruby, Cape emerald, iolite and opal.

Giant chrome diopside gem in kimberlite from Colorado.

2009-08-12T09:18:00.000-07:00

Prior to 1975, only jade and a few agates were known in Wyoming. But from 1975 to 2007, Wyoming became known as the gem capital of North America and now has a very impressive list of gemstones and the widest diverse collection of documented gems of any state in the US. A few are considered world-class and have yielded some of the largest gemstones in the world. The collection of gems in Wyoming now include agate, jasper, common opal, fire opal, precious opal, onyx, gold nuggets, Cape Ruby (pyrope garnet), spessartine garnet, Cape Emerald (chrome diopside), chrome enstatite, kyanite, iolite, ruby, sapphire, peridot, diamond, specularite, apatite, minyulite, amethyst, aquamarine, jade, almandine, chalcedony, silicified banded iron formation, jasperoid, labradorite, grunerite, amber, chrysocolla, heliodor, varisite and others (Hausel, 2008c; Hausel and Sutherland, 2000, 2006).

Get our newsletter on how to prospect, where to prospect, and what to look for. Write to us at diamondprospector@live.com and ask to join our newsletter list and get monthly newsletters free. See our companion websites at GEMHUNTER and GEOLOGY.

Our 2009 book, 'Gems, Minerals and Rocks of Wyoming' describes many of the minerals, gems and rocks found in Wyoming and will give you a start on this fun and potentially profitable hobby.

We just finished a book on gold (2011) which will tell you exactly where to go to find dozens and dozens of gold deposits. Find it at Amazon. Don't get left behind! This 366 page book tells it all!

LINKS of Interest

2009-06-28T11:08:00.000-07:00

GOLD

Prospecting for Gold

Giant Gold Deposit Discovered in Alaska
Gold Deposits in Arizona
Gold Deposits in Alaska
Gold Deposits in California

Gold Deposits in Colorado

Gold Deposits in Montana

The Seminoe Mountains gold district

The South Pass gold district

Rattlesnake Hills gold district
Eastern Arizona Gold
Douglas Creek gold placers, WY
Copper King, WY - a million ounce deposit.

DIAMONDS, DIAMONDS & MORE DIAMONDS

2008-12-31T12:41:00.000-08:00

I love searching for diamonds. My first chance to explore for diamonds deposits occurred in 1977 when I was hired by Dr. Dan Miller of the WGS to appraise the newly discovered district south of Laramie. I ended up mapping the State Line district, found 9 diamond-bearing kimberlites my first 2 years & later mapped the Iron Mountain & Sheep Rock districts and the Leucite Hills lamproite field and explored for diamonds for some US companies, an Australian company and some Canadian companies. In fact, I was promoted to US Exploration Manager and later VP of DiamonEx USA for DiamondEx Ltd (see GEMHUNTER).

I found lamprophryes in Montana & Wyoming & identified several hundred cryptovolcanic structures within & surrounding the State Line that are likely diamond deposits (these remain unexplored). A few of these include Indian Guide, Twin Mountain, Happy Jack & others. I expanded my research & found similar cyptovolcanic structures in Canada & even in the Kimberley region of South Africa. I found a major district of 50+ anomalies sitting along the interstate in the US!

Photos - Above, gem diamonds from Kelsey Lake, Colorado, vegetation anomaly over kimberlite at Iron Mountain, and exposed blue ground in highwall at Kelsey Lake. Below, 14.2 ct flawless octahedron from Kelsey Lake, aerial photo over the Ekati diamond mine in Canada (one of 5 major mines developed in Canada since 1998), carbonate-stained soil over cryptovolcanic structure, and view of one of the Lost Lakes cryptovolcanic structures.

Commercial deposits occur in placers, kimberlite and/or lamproite & I'll bet other commercial deposits will be found in lamprophryre in the future. The diamond deposits south of Laramie were in kimberlite & placers. The kimberlites are deeply eroded & spilled millions of diamonds into the surrounding streams, but no one has ever systematically looked for diamond in the creeks (even so, diamonds were accidentally recovered in Rabbit Creek 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 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? And if you find one, typically, with effort, 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-ct stone. Some believe there are no commerical deposits in this area, but all mills were so poorly designed they rejected all diamonds of any size. For example, the Kelsey Lake mill rejected anything weighing >40 cts! It also rejected most diamonds under 40 cts such that when the tailings were tested in 1997, the first sample yielded a 6.2-ct stone! 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 good diamond companies with diamond expertise were in short supply.

CAPE RUBIES, CAPE EMERALDS, GARNETS

2008-12-31T10:52:00.000-08:00

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

2008-12-31T09:49:00.000-08:00

Little was known about gold in Wyoming, thus I set out to map, evaluate & find more. I discovered gold everywhere I looked. I was amazed at how much had been overlooked. I published compendiums that are used by 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.

I have 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.

Gold photos below - 34 oz nugget (Rock Creek, South Pass), gold from Douglas Creek, and gold from Dickie Springs (South Pass).

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 RH in veins, shears, Tertiary breccias, stockworks, pyrite. I also found significant gold elsewhere in Wyoming - Seminoe Mountains, Mineral Hill, Purgatory Gulch, more.

Left - Gold at the end of the rainbow at the Duncan mine, & view of part of the auriferous shear at the Carissa - a major gold deposit with potentially >US$billion in gold.

OTHER GEMS

2008-12-31T07:57:00.000-08:00

During 30 years at the WGS, I found hundreds of deposits. How did I do this? I used geology as a guide; I looked at things differently and was motivated to look and search for mineral deposits.

While conducting reconnaissance, I discovered jasper in several old mines at Tin Cup, in an outcrop near the south edge of the Rattlesnake Hills, and found 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 I explored, I followed trends and examined geology which lead me 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, I identified more than a dozen minerals that had never been reported in Wyoming.
Above - barite from Mine Hills, Shirley Basin. Middle- a group of cabochons cut from various material. Below - beautiful jasper from Tin Cup & me standing in old prospect pit. These prospects were reported as having high-grade gold values. I found no gold & likely these were left over from various gold mining frauds and scams from the 1800s. Note the large mass of jasper to my right (probably a few tons of high quality material).

Left - Labradorite feldspar collected by Norma Beers in the road bed of Albany County 12 in Albany County. This is just one of millions of gem-quality feldspar found in this area - yet this resource remains unexplored.

OPAL

2008-12-30T15:15:00.000-08:00

A rockhound from Riverton mentioned opal south of town. The Cedar Ridge deposit lies along the highway & is cut by numerous oil field roads, no one had recognized that this place had one of the largest opal deposits on earth! A few old geological reports from 50 years ago briefly mentioned opal, so I was surprised to find opal scattered over 14 mi2, opal masses >79,000 cts along the edge of the road & common, fire & precious opal with scattered Sweetwater agate & some of the nicest decorative stone on earth. All within Tertiary age volcaniclastic sedimentary rocks that had a notable contribution of volcanic ash erupted from Yellowstone in the geological past.

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!
Photos show precious opal, Sweetwater agate, cobbles of opal in oil field adjacent to road. Below are fire and common opal

IOLITE (WATER SAPPHIRE)

2008-12-30T14:26:00.000-08:00

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.

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.

The first iolite gems cut from Palmer Canyon (PC) material (above). Below, sky blue kyanite with pink sapphire from PC Canyon, group of sapphires & iolites, the PC blue star, & mass of fresh ioite at Grizzly Creek.

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.

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.

So what did I get for finding two of the largest colored gemstone deposits on earth? My field vehicle was confiscated & I was harassed by the director of the agency and I was no longer allowed to travel and present talks on gemstones to mineralogical societies, the public, etc. Why? That is a very good question that someone needs to investigate - and I suspect they will find more than a few corrupt politicians.

RUBY & SAPPHIRE

2008-12-30T13:50:00.000-08:00

Ruby & Sapphire are beautiful stones. In 1995, I discovered my first ruby-sapphire-corundum deposit mixed with iolite & kyanite at Palmer Canyon west of Wheatland. After I recognized this association of gems with a rock type known as vermiculite, I started searching other vermiculites. It turns out that vermiculite is a alteration product known as glimmerite formed by retaining aluminum in the original rock & removing all silica (under pressure). Thus, one ends up with a rock that is essentially nothing but aluminum-rich mica. Ruby and sapphire are aluminum oxides are require high pressures and temperatures to form (as well as a good source of silicate poor aluminum). (photos above show one of the largest rubies found on earth at the Red Dwarf deposit. Sample is partially replaced by green zoisite; and a pink sapphire with excellent cleavage from vermiculite. Middle photo is a 1.1 carat ruby cut from material at Palmer Canyon and lower photo is a ruby from the Red Dwarf).

Earlier work in the Elmers Rock greenstone belt had shown rocks in the central Laramie Mountains formed at great pressures & temperatures that were high enough one might expect to find ruby & sapphire. So I was not surprised when I found these gems. Luckily, two geologists had put together a report on vermiculite in the 1940s, so I took their publication & began searching all vermiculite deposits for ruby - about 30% contained ruby! In addition to these, other rubies were found in the southern Wind River Mountains & the source remains to be found, even though some rubies found by prospectors weighted as much as 80 carats. At another deposit in the Granite Mountains, I mapped 3000 ft of ruby schist at what is known as the Red Dwarf deposit & recovered some of the largest rubies ever found.

PERIDOT

2008-12-30T12:54:00.000-08:00

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

2008-12-30T12:45:00.000-08:00

A good understanding of geology, persistence & some 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, the most recent published by Booksurge at Amazon.

MORE information at GEMHUNTER.

Some of the many gemstones discovered in Wyoming since 1977.