Saturday, July 26, 2014

Finding Gemstones - A Prospector's Guide

"Who can find a virtuous woman? for her price is far above rubies" Proverbs 31:10

[Updated, 2/8/2022]. One of great gemstone discoveries in Wyoming occurred near the turn of the 20th century when iolite was discovered in the central Laramie Mountains (Hausel, 2014). While searching for another gemstone, the author came across the first of a group of iolite deposits in the Laramie Mountains (Hausel, 2002). At the time of discovery in 1996, the author was exploring a vermiculite schist for gem rubies and sapphires west of Wheatland, when a small specimen of flawless, gem-quality iolite was spotted in dirt south of the ‘Rolf’ vermiculite-corundum prospect. Over the next few hours, the author recovered several detrital specimens of gem-quality iolite and located the outcrop (lode) containing the gemstones.

A nearly fist-size, gem-quality, 1,714-ct, iolite nodule collected by the author at Palmer Canyon in
the Laramie Range, Wyoming. Note the presence of a thin reaction rim at the right side of photo
consisting primarily of green mica. Dimensions of this specimen is approximately 3 by 4.5 inches.

After finding a small specimen of detrital iolite 
sitting in dirt in a two-track road, more detrital stones were discovered while searching for the source rock. After some time, iolite was found in outcrop as disguised grains coated by pinite, a reaction rim coating the iolite. Additionally, essentially all of the iolite gneiss was buried under a thin layer of soil. East of the discovery site, more iolite was found in the gneiss by breaking the gneiss with a sledgehammer. In addition to the flawless ‘Palmer Canyon Blue Star’, other specimens weighing a carat to several hundred carats were recovered: most gem quality.

Extraordinary color in this 12-carat faceted ruby from Palmer
Canyon, Wyoming.

Following announcement of the discovery, a prospector from Colorado filed a claim on the 
discovery and dug a trench with a backhoe. After unsuccessfully trying to find the outcrop on three different occasions, the author flagged the outcrop for the prospector, but the prospector still could not find the deposit. Finally the labeled the outcrop with flagging tape and placed a sample of iolite in a sample bag with a note ‘Dig Here!’ The prospector still missed the iolite. Apparently he was avoiding the gneiss in order to dig in soft soil. The author finally met the prospector and his partner in the field to point out the outcrop. When the prospector trenched across the gneiss, a few hundred thousand carats of iolite were exposed in about a cubic yard of material!

Iolite cross with gold and diamonds.
Much of the iolite and rock from the trench was ultramylonite (intensely sheared and granulated rock) in which the gem value of the iolite had been destroyed by tectonic grinding and crushing along a shear zone (fault). To the west at the original discovery site, this did not appear to be a problem. The author recovered a few hundred carats of very high-quality gem material from the backhoe trench as well as many large, high-quality gemstones at the original discovery site at west end. Some faceted material from the backhoe pile produced eight gems (8 to 12 carats) (Vic Norris, personal communication). So, if it was this hard to find the Palmer Canyon host rock, it should provide an indication the region likely hides more gem deposits. The presence of favorable host rocks (aluminum-rich mica schists) that have been subjected to triple point amphibolite-grade metamorphism, suggests this region of the central Laramie Mountains will likely host more iolite gemstone deposits as well as a very good potential for more ruby, sapphire and kyanite gemstones and a good possibility for other gems such as garnetsillimanite, andalusite, and staurolite

The Palmer Canyon discovery was followed by discovery of a world-class iolite deposit four miles southwest in Grizzly Creek in 2004 which included the largest iolites found on earth. This was followed by yet another iolite discovery near the Sherman Mountains in 2005 which could host the largest colored gemstone deposit ever found (Hausel, 2005, 2005a); however field investigations are needed to verify size, extent and quality of gemstones as only cursory field studies and reconnaissance were completed and only a small portion of terrain surrounding the discoveries was ever explored for gemstones. This and all other pragmatic projects was terminated by the state geologist. These discoveries could have resulted in a new industries for Wyoming which could have yielded jobs, wages, severance taxes and royalties.

A thin slice of fractured iolite from Wyoming.
Gemologists refer to the cordierite [(Mg,Fe3+)2Al4Si5O18] as iolite; but, geologists and mineralogists prefer the term ‘cordierite’. The mineral has also been called dichroite and water sapphire although these are less commonly used. 

Cordierite is often found in the vicinity of other alumino-silicate porphyroblasts (large metamorphic minerals composed primarily of aluminum and silica) such as andalusite, kyanite, staurolite and sillimanite. Iolite host rocks include alumina-rich schist (metapelite) and gneiss that have considerable mica and have been subjected to amphibolite-facies metamorphism. Amphibolite facies refers to a general range of pressure and temperature applied to rocks during recrystallization at depth. Cordierite has also been described as a replacement mineral in alumina-rich syenite-anorthosite complexes (such as the Laramie Anorthosite complex) and in shale (Kievlenko, 2003). It is noteworthy that south of Palmer Canyon and Grizzly Creek, a 350 mi2 syenite-anorthosite batholith complex crops out in the Laramie Mountains and potentially hosts the largest iolite deposit on earth. And it is likely other iolite deposits will be found in Wyoming – particularly in the central Laramie Mountains, the northern Laramie Mountains and possibly the Copper Mountain district of the Owl Creek Mountains.

Large pseudo hexagonal nodule in cordierite gneiss, Palmer Canyon, Wyoming 

Well-crystallized cordierite forms short prismatic pseudo-hexagonal crystals (six-sided) with rectangular cross sections as well as the more common form of compact, granular masses and nodules that have no obvious crystal form and found in various shades of blue, bluish-violet, gray or brown. Fresh cordierite has a hardness of 7 to 7.5 and specific gravity of 2.55 to 2.75. This hardness is favorable for durable gemstones. 

Iolite is as hard as quartz and harder than glass and tanzanite. But the specific gravity of cordierite is unfavorable for placer concentration. With this in mind, it is surprising most iolite on the market today is recovered as a by-product of placer mining in Sri Lanka. Since there is a lack of a continuous supply of iolite, it is difficult to find the gemstone in jewelry stores although it is marketed on TV. A steady supply of the gem with creative marketing strategy could result in an iolite industry rivaling tanzanite. But currently, there is no steady supply, and the gem remains greatly undervalued. To get an idea of how attractive the faceted gemstone is, it is recommended to search the internet for photos of faceted iolite

Iolite exhibits distinct pleochroism. Pleochroism in iolite results in color change from light gray, dark violet-blue, to light sapphire blue as the mineral is rotated in light. Pleochroism is pronounced in transparent specimens such that the gem will appear deep blue when viewed down the c-axis of the mineral and light-blue to light grey-blue in other orientations (Hurlbut and Switzer, 1979). These color variations are one of the attractive features of the gem and also a physical characteristic used to identify the mineral.

A flawless, several hundred carat xenoblast iolite in Palmer Canyon Gneiss.
Iolite is often coated by pinite, a reaction rim of tiny muscovite, biotite and chlorite mica that can cloak the blue gem material (Dana and Ford, 1949). Much iolite recovered at Palmer Canyon was partially altered to pinite (Hausel, 2002). Pinite is light-green due to abundant chlorite (see top photo of Palmer Canyon blue star gemstone). These pinite reaction rims coating specimens at Palmer Canyon are typically about a millimeter thick. The coating is a result of unstable conditions during the final phase of recrystallization during metamorphism. In Grizzly Creek, some iolite was later altered to limonite (FeOH) during weathering suggesting iolite in Grizzly Creek is more iron-rich than the magnesium-rich iolite at Palmer Canyon.

Transparent iolite is suitable for gems as are some translucent to opaque varieties. The luster of iolite is vitreous and when polished should become increasingly lustrous. Iolite of highest demand is deep, bright, vivid sapphire blue, although very light blue transparent gems are also very attractive. One uncommon variety of iolite reported outside of Wyoming has mineral inclusions of hematite that produces reddish aventurescence known as ‘bloodshot iolite’. Other inclusions may produce cat's eye or asterism in cabochons – none of which has yet been recognized in the Wyoming iolites, but could occur. Many Wyoming iolites have tiny mineral inclusions of mica. 

Beautiful Wyoming iolite in silver for sale on the
Iolite is a low-priced gem. Faceted gems less than 5 carats are usually less than $200/carat and may be as low as $50/carat for good, one carat stones. Gems of 5 to 10 carats can be valued in the hundreds of dollars per carat and flawless faceted stones in the range of 10 to 12 carats may be valued at more than a thousand dollars. Gemstones of more than 12 carats are unheard of on the market, but common in the Wyoming deposits. Rough material collected at Palmer Canyon and Grizzly Creek includes some of the largest iolite gems ever found: more than a dozen stones recovered by Hausel were heavier than 100 carats, with some heavier than 1,000 carats, while a few are heavier than 10,000 carats. Some gemstones left in outcrop at Grizzly Creek were estimated to be heavier than 100,000 carats! 

Iolite crystallizes in the orthorhombic crystal system and when well crystallized, cordierite occurs as pseudohexagonal prismatic twins but most often found as rounded porphyroblasts. It has common parting and fair cleavage. Being brittle, it yields sub­conchoidal fracture and resembles quartz or sapphire but can be distinguished from both by pleochroism and subconcoidal fracture. It is also distinguished from sapphire by hardness. Sapphire is harder.

Geology & Genesis of Iolite. Cordierite is formed by metasomatic processes but is stable over a considerable temperature range. In other words, the mineral replaces existing minerals with the assistance of reactive hydrothermal fluids with favorable chemistry. It is also formed by recrystallization of other minerals during metamorphism. The gemstone has been found as porphyroblasts (large crystals mixed with smaller crystals) and xenoblasts (coarse-grained rounded to nodular crystals) in some schists and gneisses, as replacement minerals in anorthosite-syenites, in vitrified sandstones in contact with basalt, and in shales altered by burning coal seams (Dana and Ford, 1949). This means that clinker deposits in Wyoming and Montana should be prospected for iolite as there is considerable clinker in the Powder River Basin. In the geological past, many coal seams at or near the earth’s surface burned worldwide as a result of spontaneous combustion and lightning strikes. The burning coal released considerable carbon monoxide, ash, carbon dioxide and other pollutants and was hot enough to melt adjacent shales to form clinker – a porous baked rock that looks similar to some volcanic rocks. On your journey to Gillette, Wyoming, look for red clinker along the highway that looks like a volcanic rock. 

Iolite porphyroblast (large crystal) in iolite gneiss, Wyoming.
Cordierite may also be found in the same rocks that contain other porphyroblasts such as sillimanite, kyanite, andalusite, biotite and/or spinel. In low- to moderate-grade metamorphosed schist (rock recrystallized at relatively low to moderate pressures and temperatures), cordierite porphyroblasts may occur in a groundmass of quartz, sillimanite, muscovite and cordierite. In other words, it may be found as large, massive, nodular crystals in a fine-grained rock matrix. In high-grade metamorphic rocks (rocks crystallized at high pressure and temperature) cordierite may show pseudo-hexagonal crystal habit. 

Cordierite may also form as a result of chloritization (i.e., it may be produced during replacement of host rocks by dark-green chlorite mica). In silica-deficient rocks (those with low silica content), it may be associated with corundum, spinel and alkali feldspar. In thermally altered rock, cordierite and corundum are incompatible and react to produce spinel and sillimanite (Deer and others, 1972; Spry, 1969). Where found, cordierite gneiss should lack garnet, since garnet and muscovite react under high pressure and temperature to produce cordierite, potassium feldspar and spinel during metamorphism.

A 12-carat raw pink sapphire from Palmer Canyon - specimen
from the Vic
 Norris collection.
Iolite is found in Canada, India, Myanmar (Burma), Sri Lanka, Brazil, Tanzania, Finland, Germany, Norway, Greenland and the United States. The principal source for the gemstone is Sri Lanka, where miners periodically find iolite pebbles in placers. Being that the gemstone is recovered as a secondary product with other gemstones, there is not a steady supply of the gemstone to jewelers.

In Wyoming, iolite has been identified in three lode deposits in Archean gneiss (>2.5 billion years) known as Palmer Canyon, Grizzly Creek and Owen Creek. A fourth deposit was recognized in the Proterozoic age Laramie syenite-anorthosite complex (~1.5 billion years old) known as the Sherman Mountains deposit. This later deposit could potentially be an enormous, disseminated to massive gem deposit based on past descriptions of the deposit and could potentially host more than 2 trillion carats of gemstones (Hausel 2002, 2004, 2006a)! Two of the other deposits (Palmer Canyon and Grizzly Creek) are poly-gem occurrences with associated gem-quality kyanite, ruby and sapphire. The Sherman Mountains deposit remains unexplored for gems even it could potentially be the largest colored gemstone deposit in the world (Hausel, 2006a). 

Palmer Canyon (N/2 NW Section 18, T24N, R70W) (42°3'25"N; 105°17'10"W) (recommended: Reese 1:24,000 scale topographical map (see Topoquest) and Laramie Peak 1:100,000 topo map). Plot the approximate location of the Palmer Canyon deposit on a copy of the Reese 1:24,000 scale topographic map using the first set of coordinates in the parentheses above. This will place you in the north-half of the northwest quarter of section 18, T24N, R70W adjacent to the Palmer Canyon Road. Look for the ‘T’ in ‘FOREST’ on the map in this section: the deposit lies just above the ‘T’ in a white area on the map. It is up to the reader to obtain permission for access. Remember, it is illegal to trespass on private property and to take minerals from a legal mining claim. 

Generalized map of Wyoming showing location of
Palmer Canyon
Use the GPS coordinates in the second set of parentheses (above) to view the deposit on Google Earth. Now you should have an aerial view of the deposit.

The deposit lies on a ridge along the southern flank of Palmer Canyon 17 miles west of Wheatland. Iolite occurs in a succession of Archean quartzofeldspathic gneiss, granite gneiss, metapelite, and biotite-chlorite-vermiculite schist north of the Elmer’s Rock greenstone belt. The deposit is accessible from the Palmer Canyon road which is paved to the forest boundary from Wheatland. The deposit lies a short distance further west (in less than a mile) along the Palmer Canyon road and is just north of the road along a short jeep trail running east of the main road.

What first attracted the author's attention to this deposit was a large rock sitting in the basement of the Wyoming Geological Survey building on the University of Wyoming campus. The rock was biotite-phlogopite vermiculite schist containing several small ruby and sapphire crystals in the matrix. There was no identification on the rock, but the author suspected it had been picked up by one of the other staff geologists at the Wyoming Geological Survey, the late Ray Harris, simply because only Ray and the author ever did any field work at the Survey. Harris was working on a project on decorative stones and had been attracting considerable interest with his work until the administration shut him down by taking away his field vehicle. 

Gem kyanite from the Central Laramie Mountains.
Anyway, the author stopped into Harris's office to get information on the rock. He asked if the rock was his and what he thought about the garnets (we should use the term boulder because Harris never took small samples) and indicated he was quite impressed by the garnets. Hausel asked where he collected the rock. 

It took a few days but Harris finally found a field note on the locality and said it came from the Rolf vermiculite prospect west of Wheatland. The author then asked Harris if he had noticed the garnets had distinct parting (garnets do not have parting). Harris indicated he had, but wasn't sure why. The author further asked, “Did you see that the garnets were hexagonal instead of isometric?” At this point, the author quit toying with him and pointed out the rock was filled with rubies (corundum) and not garnet. One cannot fault Ray for not recognizing this mineral because gemstones are rarely discussed in college and few geologists ever get the opportunity to see rough gemstones during their college careers - a major shortcoming of the university educational system. 

Ruby-kyanite vermiculite schist from
Palmer Canyon
In the 1930s and 40s, vermiculite was sought for use in fire-resistant insulation. Hagner (1944) investigated vermiculite deposits throughout Wyoming and published a short paper on the known deposits. At the location in Palmer Canyon, a shallow prospect pit was dug about 4 feet deep on vermiculite schist (glimmerite) at what is known as the Rolf prospect. Only a very small amount of vermiculite was exposed at the surface which had considerable corundum and some kyanite. After some research, The author noted the association of vermiculite and corundum (both are aluminum-rich and silica poor) and decided to investigate other vermiculite deposits and discovered five more ruby deposits in Wyoming. So, if you have any publications on vermiculite in your state, province or country, you might visit those deposits and search for ruby and sapphire.

“Search aluminum-rich rock such as vermiculite, as there is a close association of vermiculite with ruby and pink sapphire”.

Pink corundum (sapphire) vermiculite schist from
Palmer Canyon
Hagner (1944) interpreted vermiculite schist to form by replacement of biotite by hot pegmatitic fluids. Pegmatite is not found in the immediate area, so possibly hot fluids were driven off other rocks during regional metamorphism. Cordierite was not mentioned in Hagner’s report and there was no appraisal or description of corundum. 

Some samples collected from the schist by Hausel contained 2 to 20% corundum! Some corundum was gem quality and included white and pink sapphire and a few red rubies: some were cabochon grade and a few were facet grade. 

At Palmer Canyon, cordierite forms rounded to disseminated grains and large nodules: a few are inter grown with quartz. Foliation in the host rock parallels margins of nodules and in some samples terminates against nodules suggesting cordierite formed during a late metamorphic event. Kyanite and sillimanite may be present in the host rock with cordierite, but only as minor to accessory components. Some secondary calcite crusts some surfaces. 

Palmer Canyon is underlain by intercalated gneiss and schist with near vertical foliation and a N80°W trend. No exploration has taken place at depth; thus a cache of gemstones could lie at any depth. The quartzofeldspathic gneiss is the primary host for cordierite and samples contain 5 to 50% light to sky blue kyanite. 

Close up view of faceted gems sitting on the iolite
The following types of gems, near-gems and potential gem material were described at Palmer Canyon by the author: (1) high-quality flawless violet-blue, dark-blue to light-blue transparent iolite, (2) dark-gray to dark-blue transparent iolite with tiny mineral inclusions, (3) black translucent iolite, (4) low quality, dark-gray to blue-gray translucent to cloudy mylonitic cordierite (mylonite is intensely sheared and crushed), (5) red transparent ruby, (6) red translucent ruby, (7) reddish-brown translucent sapphire, (8) white to pink sapphire, (9) sky-blue translucent kyanite, and (10) common translucent cordierite with rhombohedral fractures.

It is interesting that a group of gemstones from Palmer Canyon were dressed in gold necklaces and offered to a group of women in Fort. Collins, Colorado at no cost. The gem of choice was the 3.4 carat rhombohedral fractured blue iolite (top photo to the right). This was chosen over a flawless transparent iolite and a near flawless, transparent ruby (photos courtesy of Chuck Mabarak). 

The iolite host was traced over a strike length of 500 feet and likely continues under soil for an unknown distance at both ends of the mapped area. A handful of large nodules were found during field investigation along with the ‘Palmer Canyon Blue Star’. In addition to clear, transparent, violet-blue gem-quality cordierite, some black translucent cordierite (‘Palmer Canyon Black’) was recovered. The Palmer Canyon Black is all cabochon grade. 

Much high-quality iolite rough ranges from pleasing dark blue, to violet to very light-blue color sometimes with a hint of cleavage and parting. Mineral inclusions for the most part are invisible to the naked eye although some larger inclusions are visible and form white acicular grains (possibly sillimanite) and distinct pseudo-hexagonal black biotite. 

Gray to dark gray cordierite is translucent with well-developed parting parallel to the c{001} axis and cleavage along b{010} axis. Many specimens exhibit rectangular cross sections and a few have pseudo-hexagonal habit. A group of cabochons cut from this material weighed 0.27 to 3.02 carats. These were dark-gray to black with distinct cleavage, parting and fractures. 

References Cited 

1.0 carat Palmer Canyon iolites
  • Dana, E.S., and Ford, W.E., 1932, A Textbook of Mineralogy, John Wiley and Sons, New York, 851 p.
  • Deer, W.A., Howie, R.A., and Zussman, J., 1972, Rock-Forming Minerals – vol. 1 Ortho-and Ring Silicates. William Clowes & Sons, Ltd. New York, NY, 333 p.
  • Hagner, A.F., 1944, Wyoming Vermiculite Deposits: Wyoming State Geological Survey Bulletin 34, 47 p
  • Hausel, W.D., 2002, A new source of gem-quality cordierite and corundum in the Laramie Range of Southeastern Wyoming: Rocks & Minerals v. 76, no. 5, p. 334-339. 
  • Hausel, W.D., 2004, Geological Reconnaissance of the Grizzly Creek Gemstone Deposit, Laramie Mountains, Wyoming – A Potential Source for Iolite, Sapphire, Ruby & Kyanite: WSGS Open File Report 04-14, 8 p.
  • Hausel, W.D., 2005, Geologists Locate Giant Gemstones: ICMJ Prospecting and Mining Journal, v. 74, no. 7, p. 7-9. 
  • Hausel, W.D., 2005a, Minerals and Rocks of Wyoming – A Guide for Collectors, Prospectors and Rock Hounds: Wyoming Geological Survey Bulletin 72, 159 p. 
  • Hausel, W.D., 2006a, Gemstone discoveries in Wyoming: Rocky Mountain Association of Geologists Outcrop 55:3.
  • Hausel, W.D., 2014, Finding Gemstones - A Prospector's Guide to Gemstones, Gold, Rocks & Minerals: Gemhunter Publications, 368 p. 
  • Hausel, W.D., and Sutherland, W.M., 2000, Gemstones and Other Unique Minerals and Rocks of Wyoming - A Field Guide for Collectors: Wyoming State Geological Survey Bulletin 71, 268 p.
  • Hurlbut, C.S., Jr., and Switzer, G.S., 1979, Gemology: John Wiley and Sons, New York, 243 p. 
  • Kievlenko, E.Y. 2003. Geology of Gems. Ocean Publications Ltd., Littleton, CO. 432 p.
  • Spry, A., 1969, Metamorphic Textures. Pergamon Press, Oxford, England, 350 p.
Two 4- and 6-carat faceted Palmer Canyon Black iolites 

Close up of iolite gemstone collected by the author at Grizzly Creek. This stone weighed several
thousands of carats!
A 6-carat iolite from Palmer Canyon

A 16-carat iolite from Wyoming

Group of 6 to 12 carat iolites from Wyoming

A 10-carat Palmer Canyon black cabochon

A 100+ Carat iolite from Palmer Canyon collected by Hausel

Close up of large iolite porphyroblast collected by Hausel at Palmer Canyon

Outcrop of massive iolite discovered at Grizzly Creek Wyoming by the author.
Essentially, everything in this photo with the exception of the rock hammer and 
milky quartz vein cutting through the iolite, is one, big massive polite gemstone!

Wayne Sutherland sits in front of massive iolite outcrop at Grizzly Creek, Wyoming.
This is a very sizable outcrop and likely hosts more than a million + carats of the
gemstone. With the exception of the quartz vein above Wayne's back pack, nearly
all of the remaining outcrop in the photo is iolite.

Sunday, December 9, 2012

Iolite - Extraordinary Gemstone

Beautiful gem-quality iolite in outcrop at Grizzly Creek. Note
the yellow-brown limonite adjacent to the blue iolite. This is
mineral rust: weatherediron-rich iolite has a rusty surface
and everything sitting under the rust is also gem-quality iolite.  
Note the scale on the rock, this scale is in inches.
Iolite (gem-quality cordierite) can produce beautiful gemstones with an appearance of sapphire - but with the addition of extraordinary pleochroism (this means simply that it tends to change color as the gem is rotated in light)! In 1996, the first, known gem-quality iolite deposit was discovered at Palmer Canyon in the central Laramie Mountains of Wyoming (Hausel, 1998). At the time, iolite was one of the rarest gemstones on earth. Following discovery, thousands of carats of iolite were recovered with minor pink sapphire, some ruby and considerable gem-quality kyanite. The largest known iolite gemstone in the world in 1996 was also found by the author and named the 'Palmer Canyon Blue Star' - a rough gem of 1,750 carats. Several stones of more than 100 carats were also recovered at the time.

Following discovery, geological models were developed by the author to assist in a search for similar gemstone deposits (Hausel, 2002, 2007; Hausel and Sutherland, 2000, 2006). In particular, these types of deposits (iolite and kyanite) were typically found in alumina-rich metamorphic rocks of moderate amphibolite grade. Whereas the nearby rubies and sapphires were located in a silica-poor vermiculite schist (known as glimmerite).

Using geological models, it was predicted in 2000 that Grizzly Creek south of Palmer Canyon would likely be a similar deposit as Palmer Canyon (Hausel and Sutherland, 2000). Thus in 2004, we verified my geological model and proved that Palmer Canyon contained a similar suite of gemstones including the largest iolite gemstones ever discovered (Hausel, 2004). The largest gemstone I carried out, I named the 'Grizzly Creek Blue Giant' which weighed more than 24,000 carats! But this detrital stone was dwarfed by the giant stones we left in the outcrop since we lacked the proper tools to carve them out of the hard rock.

Selection of faceted iolite and ruby gemstones from Palmer Canyon.
The Grizzly Creek Blue Giant gemstone was donated to the Wyoming Geological Survey and was put on display on the first floor of the agency at the University of Wyoming campus. If one were to assume iolite gemstones would sell for $20 to $50/carat, this one stone alone could produce $500,000 to $1.2 million in faceted gems. With some gemstones remaining in the outcrop that likely weigh hundreds of thousands of carats, the value of this gemstone deposit could be considerable.

But the discovery was followed by discovery of another giant gemstone iolite deposit by myself known as the Ragged top-Sherman Mountain deposit further to the south in 2005 (Hausel, 2005) and this was again followed by another deposit in Helleck Canyon a short time later (Hausel, 2007).

  • Hausel, W.D., 1998, Field Reconnaissance of the Palmer Canyon corundum-kyanite-cordierite deposit, Laramie Mountains Wyoming: Wyoming State Geological Survey (WSGS) Mineral Report MR98-1, 7 p.
  • Hausel, W.D. 2002, Gemstones, Semi-Precious Stones, Lapidary Materials, Ornamental Stones and Other Unique Minerals and Rocks in Wyoming, Rocky Mountain Section, Geological Society of America 54th Annual Meeting, abstract no. 33540, p. A54.
  • Hausel, W.D., 2004, Geological Reconnaissance of the Grizzly Creek Gemstone deposit – Potential Source for Iolite, Sapphire, Ruby & Kyanite WSGS Open File Report 04-14, 8 p.
  • Hausel, W.D., 2005, Geologists Locate Giant Gemstones: Prospecting and Mining Journal, v. 74, no. 7, p. 7-9.
  • Hausel, W.D., 2007, Gemstones of Wyoming - Recent discoveries: Colorado Geological Survey Industrial Minerals Forum, 12 p. 
  • Hausel, W.D., and Sutherland, W.M., 2000, Gemstones & Other Unique Minerals & Rocks of Wyoming - A Field Guide for Collectors: Wyoming Geological Survey Bulletin 71, 268 p. 
  • Hausel, W.D., and Sutherland, W.M., 2006, World Gemstones: Geology, Mineralogy, Gemology & Exploration: WSGS Mineral Report MR06-1, 363 p.

Friday, February 27, 2009


Flawless iolites (0.5 carat) faceted from
Palmer Canyon rough.
Giant iolite gemstones & potentially the largest colored gemstone deposit in the world were discovered in the Laramie Range of Wyoming in between 1996 and 2005. Gemstones weighing >24,000 carats were recovered with large masses remaining in outcrop that were estimated to include stones >100,000 carats - some possibly much larger! And this was only at the surface - who knows what lies a few inches or feet underground.

Another was found nearby but remains unexplored. But past exploration suggests it could contain > a trillion carats of water sapphire (iolite) gemstones based on surface sampling, trenching & mapping around the second world war. How could these deposits have been overlooked for so long? It goes to show that giant mineral deposits are sitting out there, right under our noses and few if any people are looking. And these are not rare discoveries. Discoveries like this happen all of the time and supports that we have barely touched the surface when it comes to mineral resources.

First group of iolite gemstones
 found and faceted in Wyoming.
One of the more exciting gemstone discoveries made in recent history of gemstones was gem-quality iolite in Palmer Canyon west of Wheatland, Wyoming. This led to a discovery of a world-class gemstone deposit at Grizzly Creek and a second probably world-class deposit at Ragged Top Mountain (which could be the largest in the world). This latter deposit could lead to its classification as one of the largest gemstone deposits ever found; however considerable field and laboratory investigations are necessary (Hausel, 2005b). 

Gemologists refer to gem cordierite [(Mg,Fe3+)2Al4Si5O18] as iolite. Geologists and mineralogists refer to it as cordierite. Cordierite typically is found in the vicinity of other alumino-silicates such as andalusite, kyanite and sillimanite. Host rocks include alumina-rich mica schists (metapelites) that have been subjected to amphibolite-facies metamorphism. Cordierite is also found as a replacement mineral in alumina-rich syenite-anorthosite complexes and in some shales.

Flawless 0.5 carat iolite gemstone
 facted from a Palmer Canyon
cordierite (photo courtesy of Chuck

It forms short prismatic crystals with rectangular cross sections as well as granular masses and nodules of various shades of blue, bluish-violet, gray and/or brown. Fresh cordierite has a hardness of 7 and specific gravity of 2.55 to 2.75. The hardness is favorable for durable gemstones. The principal deposits that supply much of the world’s market are Sri Lankan placers in spite of low specific gravity.

Iolite exhibits strong pleochroism. The gem may appear deepest blue when viewed down the c-axis and light blue to light grey in other orientations. These color variations are one of the attractive features of this gem. Iolite is often enclosed by a reaction rim of pinite (Hausel, 2002).

The luster of iolite is vitreous and when polished, it becomes increasingly lustrous. Gems >12 carats are unheard of, even so, rough material collected at Palmer Canyon and Grizzly Creek represents many of the largest iolite gemstones in the world. In Wyoming, cordierite has been found in gneiss with quartz and biotite as porphyroblasts with xenoblastic texture (Hausel, personal field notes, 1995). The geology of Wyoming near greenstone and supracrustal terrains is favorable for these and other aluminous gemstones.

Iolite is reported in Canada, India, Myanmar, Sri Lanka, India, Brazil, Tanzania, Finland, Germany, Norway and the United States. The highest quality gems are found as pebbles in Sri Lanka and as porphyroblasts in gneiss in Wyoming.

Large nodular masses of iolite were discovered in two separate deposits in Archean gneiss in Wyoming, and a giant disseminated deposit may occur in the Laramie Range anorthosite-syenite batholith (Hausel 2002; 2004; 2006a). These deposits represent the largest in the world, but remain poorly explored (Hausel, 2005b).

Two deposits (Palmer Canyon and Grizzly Creek) are poly-gem occurrences with ruby and sapphire as accessory minerals along with considerable kyanite in schist, glimmerite (vermiculite) and gneiss. The metapelites represent enclaves of aluminous schist and gneiss. A third deposit in the vicinity of Ragged Top Mountain is hosted by 1.5 billion year old anorthositic-syenitic rocks. This latter deposit remains unexplored even though minor granular gem-quality iolite was verified by Hausel (2006a). Local enrichment of iolite at Palmer Canyon and Grizzly Creek is promising. It is not uncommon to find gems of several hundred carats in both deposits with occasional masses weighing thousands of carats!
Flawless iolite of more than a carat, viewed from side held by tweezers. 

Palmer Canyon Iolite was discovered in 1995 at Palmer Canyon during field reconnaissance (Hausel, 2002). The deposit lies along the eastern flank of the central Laramie Range 16 miles west of Wheatland within Archean quartzofeldspathic gneiss, granite gneiss, pelitic schist, and biotite-chlorite-vermiculite schist north of the Elmer’s Rock greenstone belt. A shallow prospect pit was dug in vermiculite prior to 1944. Only a small amount of vermiculite was found. The vermiculite contains chlorite, kyanite and corundum. Samples of vermiculite-chlorite-biotite-corundum schist collected from a small prospect pit contained as much as 10-20% corundum. A minor amount of corundum is gem quality. Several specimens produced high-quality ruby and pink sapphire.

Cordierite was discovered in nearby quartzofeldspathic gneiss. Samples of cordierite gneiss yielded transparent cordierite grains including several weighing >100 carats. Some gneiss collected from the property contained as much as 20% transparent cordierite. The cordierite occurs as rounded to disseminated grains and large nodules. Foliation in the host rock parallels the margin of nodules and in some samples appears to terminate against the nodule boundary, suggesting that some of the cordierite formed during a post regional metamorphic event. Nearby, kyanite schist contains 20 to 50% excellent, light to sky blue with lesser tawny, green and red gem-quality kyanite prisms.

Transparent blue iolite occurs as large porphyroblasts, nodules and disseminated grains in gneiss adjacent to corundum and kyanite schist. The iolite was traced over a strike length of 500 ft and continues under soil for an unknown distance. A handful of large nodules were found at the time of discovery that include a raw, high-quality transparent gem known as the ‘Palmer Canyon Blue Star’ of 342.8 grams (1,714 carats), which was the largest iolite gemstone in the world at time of discovery. In addition to clear, transparent, violet blue gem-quality cordierite, some black translucent cordierite (‘Palmer Canyon Black’) was recovered. The Palmer Canyon Black produces attractive cabochons.

Pink sapphire, ruby and blue iolite from Palmer Canyon.
Each stone weighs 0.5 to 1.5 carats.
Much of the high quality rough material ranges from pleasing violet to a very light-blue color with only a hint of cleavage and parting. Microscopic examination shows few mineral inclusions in some gems. Gray to dark gray cordierite has well-developed parting and cleavage. A group of cabochons weighed 0.27 to 3.02 carats. These are dark-gray to black, translucent to opaque, near gems with distinct cleavage, parting and some fractures.

Two poor quality specimens were faceted that yielded a 3.9-carat lozenge-cut stone and a 3.4-carat marquise. Both were flawed with visible cleavage and parting. However, both produced surprisingly attractive jewelry when mounted in a necklace. Some bluish gray to gray translucent to cloudy material represents rehealed mylonitic cordierite that is poor-quality
A 3.4 carat cordierite with cleavage yielded a
surprisingly attractive gem when placed in a
necklace (photo courtesy of Chuck Mabarak).

Grizzly Creek Grizzly Creek is accessed from the Palmer Canyon road about 4 miles east of the Palmer Canyon deposit at the base of the Laramie Range. Following discovery of Palmer Canyon iolite, similar deposits were predicted to exist in Grizzly Creek (Hausel and Sutherland, 2000). The thermal metamorphic event responsible for the large cordierite porphyroblasts at Palmer Canyon appears to have been widespread in the central portion of the Laramie Range. The earlier prograde metamorphic event produced large prophyroblasts of kyanite in the adjacent rocks.

It became clear during the initial field investigation that a major gem deposit had been discovered. Very large masses of gem-quality iolite were found, as well as large quantities of gem-grade kyanite.

Cordierite at Grizzly Creek is surrounded by kyanite and sillimanite schists that contain minor corundum. The kyanite and sillimanite schist lies in a 300 by 5000 foot belt of metapelite. Much kyanite appears to be cabochon grade and has a very pleasing, sky-blue color, with some tawny and pink specimens.

Iolite found nearby is massive and forms large replacements of the schist. This one deposit may represent the largest iolite occurrence in the world. During reconnaissance, specimens of massive iolite were collected including one football-size transparent gemstone that weighed 24,150 carats – the largest iolite gem found in the world that now resides in the Wyoming Geological Survey museum. However, this stone is dwarfed by masses of material that remain in place in Grizzly Creek. Some of the massive gem material will require quarrying operations to recover. It is very likely gem specimens >1 ton (>4.5 million carats) could be recovered (see photo above)!

In outcrop, the iolite is weakly iron stained and shows excellent light blue color and transparency on fresh surfaces. It is not known how much if any of this material has been destroyed by mylonitization. For example, several specimens collected at Palmer Canyon showed distinct mylonitic to ultramylonitic texture in thin section that resulted in cloudy, light-blue and glassy material of 

poor quality.

Grizzly Creek Blue Giant (left) weighing in at 24,150 carats and fresh broken surface at Grizzly Creek showing gem iolite.

Ragged Top - Sherman Mountains
The first report of iolite in Wyoming was by the renown mineralogist John Sinkankas (1959). A brief description indicated that iolite was a widespread constituent of schist and gneiss. In describing this particular deposit Sinkankas wrote, “…one estimate has placed the quantity available at thousands of tons. Specimens at this locality examined by the author are glassy broken fragments of rather light blue color, verging towards grayish, small sections are clear and suitable for faceted gems. It is entirely possible that important amounts of gem quality material will be produced from this locality in the future.” Unfortunately, Sinkankas did not give a location: the whereabouts of this giant deposit remains unknown? After I had discovered the Palmer Canyon deposit, I came across this reference and called Sinkankas to get more information. However, he was unable to remember anything about the deposit - but it likely was the Ragged Top - Sherman Mountains cordierite deposit.

At the time of Sinkansas's writing (1959), only one cordierite deposit had been described in the literature in Wyoming. The deposit, known as the Sherman Mountains deposit, occurs 15 miles south of Palmer Canyon. This deposit is in Proterozoic (1.4 billion year old) metanorite, syenite and syenite-diorite gneiss of the Laramie anorthosite complex intrude the Cheyenne suture (1.8-1.6 billion years old) zone. Widespread lenticular to tabular layers of cordierite is found in metanorite (hypersthene gneiss), gneiss and syenite along the southern margin of the anorthosite complex (1.5 billion years old).

The deposit was described by Newhouse and Hagner in 1949 (see Hausel and Sutherland, 2000) for its potential to produce magnesium from cordierite. There was no mention of gemstones during this investigation, but this is likely the deposit mentioned in passing by Sinkankas in 1959 as it was the only known cordierite deposit known in Wyoming at the time.

The host rock was described by Newhouse and Hagner to have as much as 50 to 80% cordierite. The occurrence lies 0.5-mile west of Ragged Top Mountain in a belt 0.3 to 1.2 miles (0.5-1.9 km) wide and 6 miles (9.6 km) long. The host gneiss is highly foliated, intensely folded and contorted. The weathered cordierite was described to have dark brown surfaces that yield to blue or bluish gray massive material on fresh surfaces: sounds like iolite. I (Hausel) was able to collect small samples of disseminated cordierite along the margin of this deposit in a road cut. All of the cordierite I collected along the edge was very high quality and flawless gem material. The material ranged from 1 to 4 carats in weight! The rest of the deposit, including the portions described as massive remain unevaluated for gemstones and this deposit may represent the largest, colored gem deposit in the world.

During the second world war, two geologists - Newhouse and Hagner investigated this deposit and published a report in 1949. They investigated the deposit of cordierite for its magnesium content and ignored the gemstone potential. The deposit was mapped and trenched and a surface resource was estimated. The deposit was investigated and described to be scattered over a few square miles in lenticular to tabular masses in low ridges in the host rock known as metanorite. This occurred over an area of 5 miles long and 0.25 to 1 mile wide. Some exposures are described to have 60 to 80% cordierite. It was estimated at the time that the combined deposits with strike lengths of 100 feet or more, contained >453,600 tonnes of cordierite! This was only based on surface samples and trenches and no drilling was conducted to determine the depth of this deposit.

One tonne contains 5 million carats, and 453,600 tonnes contain 2,268,000,000,000 carats! If we assume that only 10% of this deposit is gem-quality, there would still have an incredible amount of gem material (and this does not include the potential resource below the surface. Just imagine how much in the way of gemstones likely occur within the first hundred feet of the surface.

Sinkankas (personal communication, 2002) indicated that much of the material was gem-quality (Sinkankas, 1959, 1964). This (along with Grizzly Creek) could be one of the greatest discoveries of colored gemstones in history. BUT, investigations were ended in 2006 as my field vehicle was confiscated and given to the WGS secretary, I was no longer allowed to present talks to the public and professional groups, and much more. Why the cover-up?

6-carat iolite cut from Grizzly Creek cordierite.
This and the other iolite-ruby-sapphire-kyanite deposits discovered in the central Laramie Range needed to be completely evaluated by geological mapping, sampling, faceting of material and drilling. Instead, all research related to these giant discoveries and the work on the giant opal deposit near Riverton, were terminated due to politics.

Owen CreekAnother iolite deposit in the northern Laramie Mountains is referred to as Owen Creek (Hausel, 2009). This contains kyanite, sillimanite, cordierite and relict staurolite in pelitic schist in this region and remains unexplored. Cordierite is also reported at South Pass (Hausel, 1991), Copper Mountain (Hausel and others, 1985), in the Sierra Madre, and in the Powder River Basin. The cordierite occurrences at South Pass were investigated by me during field mapping of the greenstone belt. I did not observe any gem-quality material in that area. However, I highly recommend investigations of cordierite at Copper Mountain as this supracrustal belt contains abundant metapelite (alumina-rich rock) that was subjected to similar metamorphic conditions as the Elmer’s Rock greenstone belt.

Flawless iolites cut from Palmer Canyon cordierite

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Iolite gemstones from Wyoming