Hints for Prospectors & Rock Hounds
By using science, a prospector or rock hound can predict where to find minerals of potential interest and then visit the field to search for other clues such as vein trends, pegmatite dike swarms, lineaments, favorable rocks, indicator minerals, etc. So listen to science (most of the time) and try to throw out that scientific crap that will lead to scientific diarrhea.
There are different levels of prospecting. At one extreme would be to search for diamonds in the arctic north. Logistics, harsh conditions and high prospecting and field expenses are expected in such regions that is beyond most of us. Nearly 2 decades ago, a group of geologists and prospectors decided Canada was ripe for a major diamond strike. They searched barren lands to the north looking for a source for many diamonds found in glacial till – and they hit pay dirt making one of the greatest finds in modern history.
This region was considered one of the better areas to explore for commercial diamond deposits in the world, but prior to 1998, no one payed any attention to Canada. After all, there were no known commercial diamond deposits. But at the same time, no one ever really looked. But the science suggested it was probably the best if not one of the best terrains to search for diamonds.
Large parts of North America (much of Canada and extending south into the Montana-Wyoming region and into the Michigan region) are underlain by a stable continental core known as a Craton. Cratons consist of older continental cores known as Archons (rocks that are >2.5 billion years old), Protons consisting of Early Proterozoic age basement rocks (1.8 to 2.5 billion years) and Tectons (Late Proterozoic basement rocks that are 1.8 to about 600 million years old). Commercial diamond deposits occur in volcanic rocks known as kimberlite and lamproite which intrude the old basement Archean cratons (Archon) and younger Protons (Lower Proterozoic belts). And of course, there are commercial secondary diamond deposits in rivers, streams and beaches that erode from kimberlite and lamproite. So - if you are going to prospect for diamonds - get to know what kimberlite and lamproite look like and where they should be found. As you scan the photos on the links, you are going to run down to Dooley's Bar and tell everyone you've seen kimberlite. But before you get into that second pitcher of beer, realize there are a lot of volcanic rocks and breccias that look like these two rare rock types. But to positively identify kimberlite or lamproite, you are also going to need to know something about the extremely rare minerals found in these rocks, their mode of emplacement (breccia pipes, dikes, sills, maar and small volcanoes) and very importantly, their rock chemistry. But don't feel lost - have another beer and realize there are many geologists who can't identify these rocks. But with some training in their characteristics, you can get a good approximation without spending $50K a year to go to college.
Using geological reasoning, the Canadian group headed to the Northwest Territories of Canada and after considerable time, discovered diamond-rich kimberlite at Lac de Gras that now is marked by one of the largest diamond mining facilities in the world. Commercial diamond production began in 1998 after more than $1 billion capitalization needed to build the mine and identify minable reserves. Because of this discovery, Canada took a major leap resulting in a major diamond industry and now has other diamond mines along with hundreds of discoveries all over the country. A good summary on the Canadian diamond industry was published in the Colorado Geological Survey 2007 industrial minerals forum “Diamond Deposits of the North American Craton”. Another paper was published by the Wyoming Geological Association in the 2008 “Topics in Wyoming Geology”.
You can actually fly on you computer to the diamond fields - just download Google Earth and search for “Ekati airport”, and you should find yourself looking in one of the most desolate places on earth with nearby circular open pit mines. These open pits did not exist prior to 1998 and the reason they are circular is because many diamond pipes are circular and look like carrots in cross section. Not so long after the Ekati was put in production, kimberlite at the Diavik Mine (now Canada's largest producer) was found and put into production (search Goggle Earth for "Diavik Diamond Mine, Fort Smth, Unorganized NT, Canada"). And others were discovered. But we all cannot spend our weekends searching the tundra of Canada for diamonds or the outback of Australia for gold, so we need to focus on regions around us to find treasures left by Mom Nature.
So, look for diamonds in the Colorado-Wyoming State Line district. As prospectors, I would not bother with the kimberlite pipes but instead, there must be millions of diamonds in streams draining the district and likely will be found in streams and gravel pits for tens to hundreds of miles downstream. Why bother with kimberlite when mother nature did all of the work for you by concentrating the diamonds in placers - and so far, practically no one has bothered to look even though many placer diamonds have accidentally been found including a 6.2-carat diamond and a 4.92-carat diamond. So, if you want treasure - its sitting in the creeks around the State Line district just waiting for you and your gold pan.
I summarized many prospecting suggestions in my books. I’m not sure how many people have been successful after reading these, but I have heard from a few. I wrote about where to find diamonds, gold and gemstones. Those whole followed directions in the books included: (1) A prospector who found nuggets and several ounces of fine gold using a hobby sluice in Strawberry Creek at South Pass over a period of a few weeks, (2) Another found precious opal where I recommended, (3) Another recovered several diamond indicator minerals in drainages adjacent to Highway 287 in the State Line district where there are no known nearby diamond pipes. This can only mean he is on the path to previously unreported diamond pipes. (4) Another was told exactly where to pan for diamonds and the next week, he gave me the first diamond he recovered. (5) Another searched the hills of North Carolina and found a nice, burgundy diamond where other gems had been found. And the winner so far, is (6) a prospector who followed suggestions in my latest book and panned out 36 diamonds with a gold pan. One weighed 4.92 carats and was classified by an appraiser as being of the highest water (ultra-clear), colorless and worth as much as $10,000 as a gemstone.
Other prospectors have also reported finding gold, opal, spectrolite, peridot, Cape Ruby, Cape Emerald, diamond, ruby, iollite and peridot where I said these gemstones would be.
But this is not the first time this has happened. While consulting for a Canadian gold mining company I told to negotiate for the Kelsey Lake diamond pipes, they did not and a short time later a different Canadian company found many large diamonds including a 28.3 carat gem. Another deposit I recommended to the same company and they didn't pick up the property. But years later, a consultant found a diamond at this deposit and also found kimberlite. I recommended to other companies to pick up gold anomalies in the Rattlesnake Hills. Two companies finally picked up these and by drilling, intersected considerable gold at depth - it is estimated at least 1 million ounces may have already been identified in this area. I searched for a giant gold deposit with six other geologists in Alaska and we are now all identified as the discoverers of this 42 million ounce gold deposit!
If you're not so inclined to risk the mosquito-infested tundra of Canada, just drive to the Crater of Diamonds State Park in Arkansas and dig for that gem you've been looking for - and you don't even have to leave pavement. Glenn Worthington wrote a book about finding diamonds in Arkansas that describes how and where to dig for diamonds. The book, Genuine Diamonds Found in Arkansas provides information about diamonds in that state as well as information about the Uncle Sam - a 40.23 carat diamond - the largest found in the US, to date. Or drive to Colorado and tour the Budweiser plant or Coors facility on your way to the diamond fields.
The following discussion is modified from PlanetNews -
Once a haven for cowboys, Wyoming was considered the poorest of all states for gemstones and rocks until recently – so what happened? Impressive jade boulders were found near Jeffrey City, but otherwise, nothing of note had been found in the cow pastures of Wyoming other than some agates, jasper, coal, oil, gas, bentonite and uranium. Then Dr. Mac McCallum and Chuck Mabarak from Colorado State University sampled a newly discovered kimberlite pipe in Wyoming. A rock sent to the US Geological Survey from the kimberlite contained several tiny microdiamonds! McCallum went on to make a name for himself and became respected internationally as one of the top diamond researchers and consultants in the world. For all of this excellent work, Colorado State University gave him the boot (makes one wonder what is wrong with Department Chairmen, University Presidents and CEOSs). Dr. McCallum also brought to light that Wyoming had a major palladium and platinum deposit at the New Rambler mine west of Laramie.
According to PlanetNews, another geologist came on the scene a little later. Just like Chuck Fipke in Canada, this geologist also dreamed of treasure. Professor Dan Hausel with the Wyoming Geological Survey became known as the GemHunter. For the next 30 years, he made new discoveries every year! Imagine one person making new discoveries over 3 decades. He put Wyoming on the Mineral Map! And what did he get for it? The Boot - just like Dr. McCallum.
People have the impression everything has been found. Not so! Discoveries were made in Wyoming every year from 1977 to 2007 because of the Professor. But when he left Wyoming - the discoveries dried up - not a single gem has been discovered since! But the Professor was not alone. Others made discoveries during this time including Ray Harris, Dr. Robert Houston, and Dr. J.D. Love!
After diamonds were accidentally discovered, more than 40 deposits were found along the Colorado-Wyoming border which yielded more than 130,000 diamonds. And more than 600 anomalies were found by the Professor that suggest Wyoming, Colorado and Montana are underlain by a diamond province of unparalleled size. Now here's where you come in. As a prospector and rock hound, start researching these and maybe you will be the next Chuck Fipke!
Back to the Professor. While working for an international diamond company, he found another group of 50 depressions along Interstate 80 within sight of the state capitol. Are these diamond pipes? They sure look like they could be. But they still have not been drilled or sampled. Earlier, the Professor was looking for diamonds in the Leucite Hills near Rock Springs but he found another gemstone everyone else missed. Peridot! He took 13,000 carats along with many angry ants from their anthills and from an outcrop at Black Rock - this was the first time peridot had been found in Wyoming!
The professor noted the diamond pipes in the State Line area as well as some newly discovered pipes at Cedar Mountain to the southwest of the Leucite Hills had other gemstones everyone again ignored. Beautiful gem pyrope known as Cape Ruby in South Africa, spessartine garnet, and gem-quality chrome diopside (known as Cape Emerald), chrome enstatite that is impossible for a novice to tell from emerald and less valuable black picroilmenite and chromite.
In 1981, he predicted gold would be found near Casper - simply by studying the geology from his desk. Then he went out to find the gold. This became one of the more impressive finds in the past century in Wyomng and will end up being a major gold mine someday. Well the professor not only found a gold deposit, he found a whole new gold district that everyone else missed.
A gold district has many gold deposits and the Professor predicted this district would have a major gold deposit along with other gold deposits. This became known as the Rattlesnake Hills district. Geologically, it is what geologists call a greenstone belt. Not only did the professor find the Rattlesnake Hills greenstone belt, he found gold at several locations. And he also mapped the South Pass greenstone belt and Seminoe Mountains greenstone belt and found gold in the Elmers Rock greenstone belt. We may never know how many gold deposits the Professor found, but it is clear he found many dozen! So as a rock hound or prospector, whenever you see the words - 'Greenstone Belt', start looking for gold. Greenstone belts are well known for gold deposits.
Following this discovery, mining companies and consultants explored the district and discovered other gold deposits. After more than 3 decades of drilling, a significant, large-tonnage, low-grade gold deposit was found at Sandy Mountain: right where the Professor told the University of Wyoming Research Institute it would be - but they would not give him money to research this prospect.
The Professor predicted at least two generations of gold were to be found - gold within the old greenstone belt rocks and gold as replacement and breccia pipes with the much younger volcanic rocks that intruded the greenstone belt. In other words, the Rattlesnake Hills has the best of both. Greenstone belts are well-known for rich gold deposits, such as the greenstone belts in the Yilgarn Craton in Australia, which hosts 30% of the world's gold reserves and 20% of the world's nickel reserves. And the associated breccia pipes related to younger volcanic rocks are similar to gold deposits mined at Cripple Creek, where more than 23 million ounces of gold have been mined. Will the Rattlesnake Hills turn into another Kalgoorlie or Cripple Creek? Well, it does have geological features characteristic of both.
After these discoveries, a few companies drilled. ACNC found more gold deposits: Newmont Gold found a million ounces at Sandy Mountain, but walked away from a $1 billion+ gold deposit. Another company began exploring Sandy Mountain and they hit more gold! Lots of gold. The Professor felt he had found a large breccia pipe between Sandy Mountain, Oshihan Hill and Goat Mountain - the mother lode but could not get State funds to drill.
Over the years, prospectors and treasure hunters found many gold nuggets in Wyoming. A 7.5-ounce nugget was found at South Pass by a rock hound. Another treasure hunter from Colorado found more than 100 nuggets. Another person from Arizona recovered 399 nuggets in the Sierra Madre, and then there was a 34 ounce nugget found in the 1930s and a boulder full of gold found before then. Yes, there is gold in the Windy state.
Over the years, a few gems were found besides jade: agates, jasper, a beautiful 2-foot long aquamarine from Anderson Ridge found by the late Elmer Winters. To find aquamarine, and I can guarantee some has been overlooked - look for granite pegmatite - very coarse grained granite! Pegmatites are easy to find and many can be spotted on aerial photos such as Google Earth. In the book Gemstones the author described many places where pegmatites are found provided GPS coordinates to many pegmatites that are mostly unexplored. In such places, one can look for aquamarine, helidor, tourmaline, spodumene, garnet and other minerals and gems. If you are interested in focusing on areas where aquamarine has already been reported, search pegmatites described in geological reports and this will lead you to places such a the Owl Creek Mountains, Black Hills, Anderson Ridge, Hartville uplift, etc.
A significant opal deposit was recently described. This opal deposit was described by geologists of the USGS in the 1930s. In their reports, they mentioned opal in passing. This area was later investigated and cobbles, boulders and pebbles of opal were found over a 16-square mile region with agate. The geology tells us that similar Tertiary age rocks containing silica-rich ash falls, found all over Wyoming and parts of Montana, Idaho, Nevada, Arizona, Nebraska and South Dakota, may have some opal. As a prospector, look at geological maps for favorable geological formations. Next, if you are inclined to read some boring stratigraphic columns, read old geological stratigraphic reports and look for any mention of opal, opalized, etc., and then go have a look. Many areas in Wyoming should contain opal based on all of the volcanic ash deposited from past Yellowstone eruptions and also from other eruptions further west. And places like Arizona should be excellent for opal discoveries.
Finding a group of major iolite deposits was very important, as these gems could potentially result in a major industry in the future. Iolite looks like tanzanite - only better to some collectors. It is an extremely rare, sapphire to violet blue gem. In 1995, the Professor found this gem with ruby, sapphire and kyanite and at the time, recovered the largest iolite gem in the world - 1,750 carats.
Then in 2004, he found an iolite weighing 24,100 carats at Grizzly Creek. There were larger gemstones but he couldn't figure out how to place a gemstone weighing more than a million carats in his back pack! That's right, gemstones so large that it will require some serious mining to get them out. He had predicted this deposit would occur based on geology and even wrote about it in 2000. Then he came across the Sherman-Raggedtop iolites. Beautiful iolite gemstones and based on geology, this one could contain more than 2 trillion carats! But the Professor moved on before much could be done on this deposit
Gold is heavy, malleable and warm yellow metal. When scratched with a knife, the yellow flake or nugget will have a distinct gold-colored indentation. Gold is also very heavy, and is 15 to 19 times heavier than water. For comparison, quartz is only about 2.8 to 2.9 times heavier than water.
In lodes, gold is often found with sulfide minerals. These may include pyrite (iron-sulfide), also known as fool's gold, arsenopyrite (iron-arsenic-sulfide), and chalcopyrite (copper-iron-sulfide). Pyrite can fool many people. It is often mistaken for gold; however, pyrite is much lighter and forms brass-colored, brittle crystals that often have cubic (6-sided) or pyritohedral (12-sided) habit. Unlike gold, pyrite is not malleable and can be easily crushed to a dark greenish-grey powder by striking the mineral with a rock hammer. Scratching a streak plate (a rough, white piece of tile) with pyrite will also leave a distinct black streak of powder on the tile.
But pyrite sometimes contains hidden gold within its crystal structure - it can hide as much as 2,000 parts per million gold (this would be equivalent to a ton of pyrite containing about 60 ounces of gold). The gold in the pyrite would not be visible; unless some the mineral had oxidized and was replaced by limonite (a hydrated iron-oxide that is essentially rust) producing what is known as gossan, or boxworks.
A gossan is essentially a reddish- to yellowish-brown, iron-rich mass found in some veins and faults. Gossans provide excellent places to search for gold, since limonite produced by the oxidation of gold-bearing pyrite, may contain specs, rods, or masses of visible gold. The better places to look for visible gold in gossans are in web-like, honeycomb, vuggy zones known as boxworks. Boxworks result from oxidation and removal of the pyrite, leaving behind silicified ridges, or outlines of the former crystals. Gold, however, being relatively inert, will remain in place, and can sometimes be found on the boxwork ridges.
Other sulfides found with gold include arsenopyrite and chalcopyrite. Arsenopyrite, a brittle, silver-metallic, mineral, will oxidize to a greenish-yellow limonite known as scorodite. When arsenopyrite is struck with a rock hammer, a garlic odor will be detected. This is due to arsenic in the sulfide. Some arsenopyrite can potentially hide as much as 1,000 ppm gold in its crystal lattice.
One mineral that is more often mistaken for gold than pyrite, is mica. Mica is often found in both lodes and placers. Each year dozens of people bring samples of mica to the WGS believing they have found the 'mother lode'.
In general, gold is found in lodes and placers. The term 'lode' simply describes an in situ mineralized vein or fault as opposed to a placer, which consists of reworked, detrital, heavy minerals concentrated in active or inactive stream gravels. Veins generally form narrow sheets of quartz, whereas most faults consist of vertical to near vertical sheets of intensely deformed rock that often contain quartz veinlets and boudins (lenses). When mineralized, the gold values in lodes are typically erratic along much of the length of the structure and random sampling may yield only trace amounts of gold. However, periodic ore shoots (enriched zones) are sometimes encountered. Some of these pockets may average more than 1 ounce of gold per ton. At such high grades, the gold will often be visible to the naked eye and individual pieces of rock may produce specimen-grade samples, especially when ore grades run higher than 1 ounce per ton.
Gold has been found in all of Wyoming’s mountain ranges as lode and/or placer deposits. Some of the better places to search for gold include the Wind River, Seminoe Mountains, Medicine Bow Mountains, Mineral Hill, and Sierra Madre.
The best place to search for specimen grade gold samples in Wyoming is the South Pass district, along the southeastern margin of the Wind River Mountains. The district encloses several gold-bearing faults (shear zones) and some veins. Many of these are located on maps published by the Wyoming Geological Survey, and there thousands of feet of gold-bearing shears in this region that have never been seriously prospected!
This area is also a good place to search for specimen-grade samples. For example, some ore recovered from the Carissa mine in 1908, assayed as high as 260 ounces per ton gold. The Miners Delight mine at South Pass was also a fairly good source of gold. Downslope from the mine, historical reports indicate that water was pumped from the shaft and used to mine Spring Gulch. Several 1 and 2 ounce nuggets were found in the gravels including one 6 ounce nugget. One lump of specimen-grade quartz was found in 1873 that was as large as a water bucket. According to one witness, it looked as if it contained a pound of gold. In nearby Yankee Gulch, northeast of the Miners Delight mine, 8 to 15 ounces of gold were mined per day including one nugget that weighed nearly 5 ounces.
In the central part of the district, the Rock Creek placer produced one fist-size chunk of quartz filled with an estimated 24 ounces of gold. A boulder found nearby in 1905, contained an estimated 630 ounces of gold!
Within the South Pass region, is the Lewiston district, located east of the South Pass District. In the 1890s, a 500-foot strip of gravel was mined at Wilson Bar along the Sweetwater River within the district, and yielded 370 ounces of gold. The gold was traced upstream to a lode named the Burr. In 1893, a pocket of ore intersected at the Burr lode yielded 3,000 ounces of gold. Some samples from this pocket was claimed to have assayed as much as 1,690 ounces per ton of gold! To the northeast, another lode named the Hidden Hand produced an ore shoot that yielded several sacks of specimen-grade ore containing 75 to 3,100 ounces of gold per ton! In recent years, some samples collected to the northeast of the Hidden Hand at the Mint-Gold Leaf lode assayed 1.29 and 3.05 ounces of gold per ton.
West of the Mint-Gold Leaf lode is a short drainage known as Giblin Gulch. The gulch cuts across the western end of the Mint-Gold Leaf shear zone, and drains into Strawberry Creek. In 1932, several nuggets were found in the gulch including some that weighed 5.2 and 5.3 ounces. Other nuggets found in this area included two that weighed 3 and 4.5 ounces. These were found in Two Johns Gulch in 1905. Another report indicated that five 'good-size' nuggets were found in the Big Nugget placer in 1944. The locations of the Big Nugget and Two Johns gulches are unknown, but possibly these are the same as Giblin gulch.
Douglas Creek district. A popular place for placer mining is Douglas Creek in the Medicine Bow Mountains of southeastern Wyoming. Gold nuggets in the area are typically jagged, suggesting that they were derived from nearby lodes. Many nuggets found in the creek and its tributaries are typically coarse and jagged, suggesting they had been derived from nearby lodes (the largest reported nugget weighed 3.4 oz). In recent years, several nuggets (0.5 to 1 inch in length) were reported from nearby Bear Creek which drains into Douglas Creek. Along the eastern edge of the district, nearly 40% of the gold recovered in Spring Creek, was in the form of coarse nuggets (a 2.5 ounce nugget was found here in recent years). If you prospect in this district, you should also keep an eye out for diamonds and platinum nuggets. Both have been found in nearby streams.
To the north of Douglas Creek, is the Gold Hill district. Some specimen-grade samples have also been reported in this district in the Medicine Bow Mountains. Samples collected from the Acme mine in the past reportedly assayed as high as 2,100 opt! Specimen-grade samples from the nearby Mohawk mine reportedly assayed as high as 1,450 opt!
Seminoe Mountains district. The Seminoe Mountains lie near the central part of the state northeast of the town of Rawlins and north of Sinclair. On Bradley Peak, at the western end of the range, a small group of mines were dug on narrow quartz veins. Several specimen-grade samples of gold-bearing quartz were found on the mine dumps by Professor Hausel in 1981 which lead to a gold rush. For several weeks, every motel room in Saratoga and Rawlins was occupied from geologist from around the world trying to get the first claims in this area. Deweese Creek, which drains the Penn mines, shows very little evidence of placer mining. But based on the number of samples found with visible gold on the mine dumps, this creek probably contains some gold.
Platinum-group metals are closely associated with ultramafic rocks with high magnesium content, particularly those that are enriched in olivine, such as peridotites. A peridotite is a dark-greenish rock composed almost entirely of olivine with lesser pyroxene. Peridotites alter to serpentine, thus when prospecting for platinum, the prospector should investigate rocks described as ultramafic, peridotite, or serpentinite.
Platinum and palladium may be found in nuggets, grains, and flakes, and in certain sulfide minerals such as sperrylite (palladium sulfide), or may occur as impurities in some copper-sulfide minerals such as covellite.
Platinum-group metals have been mined from peridotites, nickel-copper-deposits in alkaline igneous rocks and in thick gabbros. However, the major platinum-group metal deposits are found in layered, mafic complexes such as the Bushveld complex, South Africa, and the Stillwater complex, Montana.
Platinum-group metals have been found in both placers and lodes in Wyoming. Platinum found in the Douglas Creek district occurs as grains or flakes. Platinum in nature has a specific gravity in the range of 14 to 17. One common impurity is iron: when in sufficient amounts, it may cause the platinum to be weakly magnetic. Platinum is a malleable, tough, bluish-gray (steel-colored) metal. It has a very high melting point, and is not affected by an ordinary blowtorch. It has a hardness of 4 to 4.5, and produces a shining silver streak when scratched by a knife.
Platinum and palladium may occur as impurities in gold, producing what is known as white gold. This has a similar appearance to amalgamated gold. But unlike most amalgamated gold, white gold will have a consistent color throughout the metal. Whereas amalgamated gold may only have a bright silver rind produced by mercury that is distinctly gold-colored on the interior of a nugget.
Lode deposits of platinum-group metals are often found in layered mafic complexes. Currently, several platinum, palladium, and nickel anomalies have been recognized in southeastern Wyoming, in an extensive region that covers three mountain ranges paralleling a major fault zone known as the Mullen Creek-Nash Fork shear zone (also known as the Cheyenne Belt).
Some of the better anomalies have been identified in the in the Medicine Bow Mountains in Lake Owen and Mullen Creek layered complexes, and the Centennial Ridge district, and in the Puzzler Hill area of the Sierra Madre to the west.
The New Rambler mine, located along the northeastern edge of the Mullen Creek complex, was one of the only known mines in North America that produced platinum and palladium during the early 1900s. A cupriferous gossan was discovered here near the turn of the 19th century. A shaft, known as the New Rambler shaft, was sunk on the gossan. Ore from the mine included many copper minerals including platinum-bearing covellite and chalcocite, with some veins containing a rare mineral known as sperrylite. Nearly all of the important work on the New Rambler mine was done by Dr. McCallum.