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Friday, April 29, 2011

Gold Occurrences in Oregon

In 1964 the author spent some time as a prospector looking for gold in southeastern Oregon on down by the Nevada border. Although we didn't see much gold we had a good look at the Oregon desert.

Map of Oregon showing the High Desert
By Oxygun

According to the geology reports there is plenty of gold in Oregon it just depends on where you look. Gold and other minerals of interest are found throughout the state, but the northeastern part of the state has produced more Gold placers. Gold mining was occurring in Oregon as early as 1859 when the first goal strike happened. Most of the rivers and streams in Oregon carry placer gold; another place where placer gold is found accompanied by about 10% platinum is in the black sands found on the beaches of the Pacific Ocean.

Panning for gold in a stream.  USFS

What you should do is try panning for gold in a likely looking stream for starters. The best kind of stream to find gold in is what might be termed a babbling brook with lots of boulders and rapids and other places where gold may be entrapped. You can usually find gold on the inside of bends on what is called the point bar. Gold is also found behind a boulder or any place where the water changes velocity from fast to slow. Generally any place where Swiftwater trout would be found is also a good place to look for gold.

Two of the best places where gold may be found in a stream is where the water runs over a ledge in the stream causing the gold to be caught in cracks on the rocks. The other place is in the plunge pool beneath a waterfall.

One of the best places to search for gold in Oregon is in the northeast quadrant of the state. This part of Oregon is mostly desert, and because of the arid conditions water is apt to be scarce for gold panning. A gold pan works almost as well in the desert as it does in more humid places where water is abundant; the difference is you don't have any water to help of the panning process otherwise the process for finding gold is practically the same.

This is what you have to do to dry pan. Fill your gold pan about half full of gravel and go through the same motions that you would if there was water in the pan. That is shaking the pan horizontally so that the larger stones and pebbles come to the top. You’ll have to pick them out by hand almost the same way that you do with water. Keep working the pan until all you have left is sand.

Now you are ready to work the sand down into a concentrate. Holding the pan so the internal riffles are facing you and slowly by rocking the pan back and forth while the excess sand pours over the edge of the pan. In this manner you can work the sand down until there isn’t really anything left but the black sand concentrate that you can take home and work over at your leisure.

This is a thunderegg collected in the Blackrock Desert.
Photo by David Rix Eibonvale

There are other minerals of interest in Oregon among them are agates and thundereggs. These stones are usually associated with flows of basaltic lava. It is in the cavities and gas bubbles in the lava that the agates and thundereggs are formed.

Most of these thundereggs are found in gravel where they have been washed out of the basalt cliffs. The thunder egg have a crust that is kind of nubbly looking. Once you see one you will always be able to recognize another. Agates and thundereggs are very hard to see in nature, but there is a way to lure them out of their hiding place. Using a spray bottle filled with water spray the gravel in front of you and if there are any agates were thundereggs there. By being soaked with water will make them stand out against the other stones like a neon sign.

Thursday, April 28, 2011

Gold Producing Metallogenic Provinces and Epochs (MPE)

There are many metallogenic provinces and epochs (MPE) that can be traced through the formations of various rocks including those particular places and times when gold was deposited. There are at least eight of these episodes that can be found in the Appalachian Mountains of southern Québec. These MPE's can range all the way from the Grenville orogeny that occurred around 1.2 million years ago, and can be traced to different types of orogenies and mineralization to the end of the Permian era. 

A map of selected worldwide ore deposits of metals.

The different MPE's can be directly related to specific orogeny like the Grenvillian or any other orogenic event that has happened in the history of the world. An MPE can be found anywhere on the face of the earth. That means you had better know the geological history of the area where you are prospecting, and remember that some orogenic events left more gold behind them than others.

MPE's are usually associated with a suture zone where one tectonic plate has collided with another. In the case of an oceanic plate colliding with the continental plate the oceanic plate is subducted beneath the continental plate, and about 20 km inside account metal plate there should be a line of granitic intrusions.

The subduction zone acts as a giant heat engine melting the material that has been dragged downward by subduction causing it to become heated to the point the material is melted.  The subducted material is also saturated with water that lowers the melting point of the material, and supplies the water that at depths of kilometers beneath the surface of the earth becomes super heated water that is capable of dissolving many minerals that when they reach the right environment through the action of the superheated hydrothermal fluid are deposited as ore.

A subduction zone.
By A.J. Stern

Searching around in the area that has been intruded one is apt to find gold in the aura of contact metamorphism that is associated with the granitic intrusions. In this case gold is often associated with scheelite, an ore of tungsten in the form of tungsten carbonate. This occurrence is often found where the granite has intruded through an older layer of carbonate rocks such as limestone or dolomite where it forms a skarn..

On the oceanic side of the subduction zone are found many metal sulfide deposits where this whole deposits are usually found in small amounts, but there can also be some really huge deposits of sulfide that are formed this way. These are the result of sulfide deposits that are laid down by black smokers found on spreading centers located on the bottom of the ocean. These deposits are laid down very much like plums in a pudding at the scattered across the bottom of the ocean.

A black smoker at a spreading center at the bottom of the ocean. NOAA

As these deposits are carried away from the spreading center by the action of more magma being injected they cover the ocean bottom with spots where they are eventually subducted beneath a continental plate where they are often reactivated to form secondary mineral deposits sometimes in quantities large enough to form ore deposits.

MPE's are where ore deposits are typically found, and in many cases are considered to be the primary source of mineralization, and they eventually break down to form detrital mineral deposits.

Tuesday, April 26, 2011

On Buying Gold Mining Stock

Yes Virginia you can make money with mining stock especially with the so-called penny stocks, or as some people call them the penny awfuls. In other quarters they are also known as cats and dogs; regardless you can still make money from them providing you do a thorough job of research first.

A core drilling rig in action.
Photo by Andrew Wood

When the author first started investing in penny stock he was inexperienced and he sure had his share of cats and dogs before he finally learned the ropes about investing in the stock. Nonetheless, it was a very expensive learning process.

Lesson number one: is that all miners are not equal! Some of these miners have developed the knack of finding valuable mineral deposits; there are others that couldn't find a dog with wet paws by following his tracks across a clean kitchen floor. From this it is quite obvious that the very first thing you should do is to become acquainted with whom those miners are that have the knack of finding a valuable mineral deposit that can be developed into a mine.

Lesson number two: this one came straight from Mark Twain, remember that a mine is nothing more than a deep hole in the ground with a damned fool at the bottom, then another damned liar at the top. You should remember that all Mining reports are based on the idea of attracting investors for the most part. In this case you should do your own due diligence rather than swallowing everything hook, line and sinker that your broker tells you.

The Argo Mine in South Africa

Lesson number three: there are usually two peaks in the life of a mining stock the first one is when the initial announcement of the discovery is made. The other peak is when the discovery actually becomes a producing mine. There are sometimes when the announcement of gaining a large amount of new capital or merging with one of the major mining companies will also produce a peak.

Lesson number four: The majority of the small mining companies are actually involved in exploration that gives them a negative cash flow until they discover something they can go to the bank with. For every 300 mineral deposits that are found by an exploration company there is only one of these discoveries that can eventually be developed into a mine. One almost heartbreaking things to do is to discover a large mineral deposit, as the author did many years ago, that can't be developed into a mine because the cost of transportation is higher than the value of the mineral deposit.

Lesson number five: How you do your due diligence is pretty much up to you, but it is very helpful to at least have a working knowledge of the geology of or deposits. Strangely, the author has discovered that at least in Canada one of the best places to gain mining knowledge is in the local Tim Horton’s. You would be completely amazed at what you can learn over a cup of coffee and donut in one of these places. The author learned of a major gold strike in West Timmins, Ontario a year before it became public knowledge.

Lesson number six: there is a saying among old-time prospectors and miners that the best place to look for new mineral deposits is under the shadow of some old mines headframe. If they are available a great deal of knowledge can be learned by reading local histories. If these are not available you should at least read about as much of the geology of the local area you can find. These reports are available from the geological survey in the area where you are interested.

Yes Virginia, you can make money with mining stocks but the primary thing is to be careful, then perform a thorough due diligence first.

Monday, April 25, 2011

How to Blast a Tunnel in Rock

Blasting a tunnel into solid rock is a process that is often encountered in mining. In performing this, the very first thing you have to remember is that any shot obeys the laws of fluid dynamics. The shot is made up so there are four large round holes at least 2 inches in diameter in the center of the shot pattern. These large holes are arranged in a diamond shape that is about 6 inches between centers, and are left empty. The four large center holes are left empty so that the shattered rock from the subsequent blast will find its way towards the center of the tunnel.

An abandoned mine tunnel
Photo by J. Smith

The remaining holes are arranged in a concentric pattern around the center.
With the use of millisecond delay caps fired electrically it is possible to cause explosions in a concentric circle with the individual shots delayed just enough so the action of the explosion by obeying the laws of fluid dynamics will cause the rock fragments to be sucked out into the tunnel away from the blast site.

In this case you can arrange the holes keeping in mind that 1 pound of modern explosives will remove approximately 1 ton of rock. A cubic foot of rock weighs approximately 2800 pounds allowing you to calculate the shot pattern based on the amount of explosives that are used. In most tunneling shots it is very rare to use holes that are larger than 1 inch in diameter, and 6 to 10 feet deep.

A tunnel inside a salt mine.
Photo by Ealdgyth

The process of removing the rock that was shattered by the shot is called “mucking” and the shattered rock is called “muck.”  All the shattered rock has to be removed, or mucked before placing the next shot. It is important to make your tunnel slightly larger than its intended size by a few inches to allow for the variation in the way rock is shattered by the blast.

You can get additional information about blasting in general, or blasting in particular from your local explosives dealer. He will also have books available on the subject, or at least can tell you where to find them. Most of these books will tell you how to blast in any situation, and explain how to set the charge, what explosives to use and what type of blasting caps or other devices to initiate the charge.

As a consulting geologist while working with blasters I often had to design charges for specific types of blasting; humbling was one of them. A lot of this experience was gained through highway construction or Quarrying projects.  The largest blast that we presided over was128,000 pounds of powder that was shot all at once. We literally tore out 1/2 mile of ledge with this single shot.

Sunday, April 24, 2011

Gold Occurrences in Washington State

Although Washington State has never been noted as a major gold producer it has however produced over 2,000,000 ounces of gold. It has been reported that the state still possesses many unexploited virgin placers as well as lode gold where it is still possible for a prospector to make a profit. The state Department of Natural Resources, Geology and Earth Resources Division in Olympia has produced a bulletin titled, “Inventory of Washington” by Marshall T. Hunting that you will find invaluable in the search for gold.

Mt Olympus on the Olympic Peninsula of Washington.

Many of the counties of Washington were gold is already been found include Ashotin, Benton, Chelan, Clallam, Clark, Columbia, Cowlitz, Douglas, Ferry, Grant, Grays Harbor, Jefferson, King, Kittitas, Lewis, Lincoln, Okanogan, Pacific, Pend Oreille, Pierce, Skagit, Skamania, Snohomish, Stevens, Whatcom, Whitman and Yakima. In many of these counties the discoveries include both placer and lode gold.

In the state of Washington the major gold producing areas are pretty well limited to the northeast corner where the gold is found in the Okanogan Highlands that expense offered from British Columbia, and contains the second largest gold mine in the United States, the Cannon Mine that produced most of the lode gold found that Washington. A far greater amount of gold has been produced from placer deposits far exceeding the amount of lode gold that has been recovered.

The state of Washington is actually composed of several different so-called suspect terranes that have been plastered onto the West Coast of the United States so the bedrock back of the state resembles a patchwork quilt. Some of the best places to recover gold is in aureoles around volcanoes that are found in the state in abundance. The driving force behind all of this volcanic activity is the “Juan de Fuca” plate that is being thrust under the state of Washington creating a range of mountains to the west of Puget Sound that are called the Olympic Mountains. It is the same plate that further inland is creating the Cascade Range that includes several volcanoes including Mount Rainier, and Mount Saint Helens.

The southwest corner of Washington is covered by the Columbia Plateau basalts that are over 3000 feet thick. The basalt flows were in place during several different episodes possessing a magma that was quite runny. It is beneath these flows that they have discovered natural gas, and there is a good possibility that gold may be found in the older rocks under the basalt covered. At the present time however we just don't have the ability to prospect for the gold because it is buried so deep under the basalt.

A typical beach on the Olympic Peninsula where gold may be found.
Photo by John Hunter

There are many reports of gold being found in the rivers that drain the Olympic Peninsula as well as the beaches facing the Pacific Ocean where fine gold has been found in the beach sands, and has produced many profitable claims. It would be advisable to check the regulations imposed on gold mining along the state beaches before you start mining. Most of the gold found on the speeches is very fine, but periodically is renewed by the action of storm waves making for a practically never ending supply.

Friday, April 22, 2011

Gold, Uranium and Carbon in Detrital Deposits

One of the common associations with gold in detrital deposits is the association of gold with uranium and carbon. This holds true in the Witwatersrand and all the other gold deposits of a detrital nature.  For many years the origin of the carbon was hotly debated with the most recent evidence holding that it is from primitive life forms that lived in the distant past in the Archean

Algae exposed at the intertidal zone similar to the ancient algae that trapped gold.  Even today this kind of mat could be a good place to search for gold.
Photo by Leonardo de Jorge

It has been posited that these algae formed great mats similar to stromatolites that acted as a trap for the gold particles and uranium minerals in the same manner that modern mats of algae work to snare gold particles in a modern environment.  It is common practice to use an artificial mat of the same nature in a sluice box to entrap gold.

Although the deposits can be several thousand feet deep now, but at the time of depositation they were relatively shallow at the bottom of running water that was only a few tens of meters deep subsequent Earth processes have buried them to their present depth. 

An angular uncomformity with a basel layer of conglomerate that would be a good place to look for gold.   The best place is right at the uncomfority.
Photo by Lamprus

At the time many of these gold bearing deposits were at the bottom of a braided stream channel that by being deposited in this manner explains the stringers of gold found in such a deposit.  These stringers of gold are common in detrital gold deposits.  Sometimes there is a layer of carbon that is as thin as a pencil line that is so rich in gold and other minerals that they are mineable. In many detrital deposits the slim lines occur at a regular frequency to the extent that the entire deposit is mined so that I can undergo further ore dressing to free the gold so it can undergo even further treatment usually by being leached with a solution of cyanide.

Even today if you encounter a mat of algae in the bottom of the stream or river is a good place to search for gold that has been caught in the mat by the action of running water.

Gold Occurrences in Idaho

According to the latest news about gold mining in Idaho, Premium Exploration Inc. (CVE:PEM) have focused their efforts on emerging gold district in Idaho in an area known as the Idaho Gold Project this is a district sized property that is seen over 13,000 m of recent drilling. This area is found in the Orogrande shear zone is a significant regional structure and also the conduit for multiple zones of gold mineralization. In many respects it is similar to the gold deposits found in the Carlin trend of Nevada. At present the Idaho Gold Project is 100% owned by Premium. At the present time Premium is working on an updated resource estimate along with a comprehensive 25,000 m drilling program.

A Yankee Fork Stamp Mill used to process gold and silver ore at the Custer Mine in Idaho.
Photo by Tinosa

The so-called Idaho Gold Project is located in Central Idaho as an epithermal deposit in the Cretaceous Idaho batholith and Precambrian basement rock where it is the conduit for alteration and extensive mineralization. It is also gone through several intrusions of rhyolite, dacite and trachyte during the Eocene. 

There was a considerable amount of placer and lode gold in the area from the 1860s until the 1930s. During that time it produced over 8,000,000 ounces of gold, and had over 20 historic mines. It wasn't until the 1970s however before modern mining and exploration techniques occurred within the area.

In 1940 report was good to go on their Idaho, C.A. Bottlfsen that was titled, “Mining Activity on the North Fork of the Clearwater River Area.” This report generated a considerable amount of interest in the area of the Clearwater River as well as Clearwater and adjoining counties in Idaho. This area is drained by the gold bearing Clearwater River and its tributaries.

The Argo Gold Mine and Mill in Idaho Springs.

The gold prospecting in Idaho usually lasts from roughly April 1 to November 1, clever if there's an open winter the prospecting season can be extended. The availability of water to carry on prospecting activities often dwindles after mid-June unless the prospector carries water to the prospecting site.

It isn't for nothing that Idaho was called the Gem State because it is the producer of many gemstones as well as gold and silver. Up to this point most of the gold that has been produced in Idaho comes from the upper part of the panhandle where it is found that placer deposits containing many gold nuggets.  The town of Murray is one of the best places to prospect, and because nuggets are so common you should come with a metal detector.

There was a time of Murray on a hotel owner wanted to go prospecting, but decided it was too cold outside. His solution was to cut a hole in one of the bedroom floors where he then go down 30 feet to bedrock to get at The gold. Another mine in the area of Murray was named the Jackass Mine that was literally found by a miner’s donkey. This is the kind of mining lore you can expect to hear in Idaho.

Two of the areas where you’re most likely to find gold are at the forks of the Pend Oreille River However, the hottest spot in the state is Boise County that has produced over 3 million troy ounces of gold from the 300 square miles of gravel that is found in the county. It would be a good idea to check out all watercourses and gravel arroyos to the northeast of Boise and close to Idaho City.

It is interesting to find the area around Boise is in a geothermal area that supplies the city with a large quantity of geothermal heat. The same area is also a place where gold is being actively deposited in areas where the geothermal liquids dropped below 200°C. It is common to find nodules of silica when you are digging within the area that in many places appears to be waterlogged. There are also known to be diamond bearing kimberlites in the same area, so you have your choice between gold and diamonds.

Boise County is not the only place where you can find gold in Idaho. The following counties are also listed for placer gold mining: Ada, Adams, Bingham, Blaine, Bonneville, Camas, Clearwater, Custer, Elmore, Idaho, Kootenai, Letah, Lemhi, Nez Perce, Owyhee, Power, Shoshone and Valley. It would be a good idea to check the watercourses and gravel arroyos found in these counties.
Aside from the gold that is found along the Clearwater River and its tributaries this river also produces star garnets that produce a star effect when cut en cabochon. The only other place where garnets like this are found is some locality in India. Jasper is found here also with at least one of the mines open to the public is the jasper mine at Willow Creek.

Idaho produces large quantities of precious opal of both faceting and cabochon grade. that displays a considerable play of color. One largest opal mines in the United States is located in northeastern Idaho called the Spencer Opal mine it is largest in the state.

Information about these mineral deposits in Idaho is available from different state and federal agencies. Sometimes you can find local history books to discover what kind of minerals were mined in a particular town.

The type of mining that went on in Idaho makes the use of a metal detector practically a necessity. Different manufacturers actually produce metal detecting instruments that are capable of detecting gold. Many of the gold nuggets that have been found are actually the result of metal detectors. A particularly good area to investigate is old mine tailings from dredge operations like the one in Boise County

We recently became a dealer for the Garrett line of metal detectors and other gold mining equipment including gold pans and gold panning kits.  Please watch for future announcements about the Garrett line of products.

Meguma Gold of Nova Scotia, Canada

Meguma gold is why I live in the United States instead of Nova Scotia because during the Goldrush that occurred in Nova Scotia in the 1860s my great grandfather as a young man was prospecting for gold in a place where he shouldn’t been prospecting on the Queensland.  The Queensmen took a dim view of these proceedings, and old stories handed down in my family were to the effect that the Queensmen wanted to invite him to a “necktie party” he was to be the guest of honor. Needless to say he left Nova Scotia quite hastily for New York where he worked as a miner at the Tilly Foster iron mine.

The Tilly Foster Iron Mine in Brewster, NY as it appeared in the 1880s.  This is the mine my great grandfather worked in when he arrived in the US from Canada.

The Meguma terrane is one of the suspect terrenes that is exposed in the southern part of Nova Scotia when it became attached to the North American craton during the Appalachian orogeny where it is joined in Nova Scotia along the Minas Fault Zone that runs east and west across Nova Scotia from Chedabucto Bay to Cobiquid Bay and the Minas Basin. Throughout the area there are a number of granite intrusions that range in age from Devonian to Carboniferous. Although the extent of the Maguma is not clear there are many geologists who believe that a magnetic anomaly that runs along the coast of Cape Cod in Massachusetts may represent a suture zone between the Maguma and Avalon terrenes.

Unlike the Avalon terrane since been definitely associated with land across the Atlantic Ocean the Maguma terrane the Maguma terrane remains a mystery that has not been associated with any land on the other side of the Atlantic Ocean. Even today there are many competing theories as to their origins that are prevalent among geologists. Many of these theories seem to feel that it was separated from Gondwana although there are plenty of other competing theories that it may have been a part of Portugal and Spain.

This is the Ccharbon Mine at Glace Bay NS where my great grandfather worked as a mine rigger before he came to the States.  The product being mined was bituminous coal.  

This area appears to be of interest geologically not only to students of geological history, but because the attendant metamorphism has produced gold deposits that were mined extensively during the latter part of the 19th century, and which remain even today as a source of potentially viable gold deposits.

One geologist that is a friend of mine had for his first assignment in the field as a geologist after graduating from college had to make an assessment on one of these old gold mines. It appeared that the Nova Scotia highway departmental head used the tailings from the mine to pave the roads in the area. His final report to the Mining Company stated that, “The roads in Nova Scotia are paved with gold.”

Gold crystals found on quartz.
Photo by Rob Lavinsky

Gold founded the Maguma terrane according to geologists that have made it a study represent concentrations of a wide variety of gold bearing quartz veins that are found in lower Paleozoic metaturbidites that are found in Southern Nova Scotia where there have been over 30 deposits of this type. Extensive studies of the fluid inclusions found in the quartz indicate that the mineralization occurred at about 370 million years ago that was related to widespread incursion of both mafic and felsic magnetism into the crust at the same time when a sub vertical shear zone was developing. This was during a time that post dated the Acadian Orogeny making them at least partially exotic to the Maguma group. Much of the mineralization in the group is considered to be either late stage magmatic fluids, then infiltrated the Maguma groups that are sedimentary rocks as the sole source of vein components that invalidated earlier sources of hydrothermal fluids.

Thursday, April 21, 2011

Gold Occurrences in Montana

Most of the Gold in Montana is found in the western half of the state where it was discovered in 1852 on Gold Creek in Powell County. Very rich deposits were found in 1863 in Creek near Virginia City created a gold rush. Since that discovery Montana has produced over 17,752,000 ounces of gold that is ranked as the seventh largest gold producing state in the United States. Most of the gold produced in Montana is a byproduct of the copper industry. Some of the best places to prospect for placer gold in Montana are located in Broadwater County on the eastern slopes of the Elkhorn Mountains in the rivers and streams that flow toward the east.

Elkhorn Mountain in Montana. Placer gold is found in the rivers draining the eastern slopes of the Elkhorn Mountains.
Photo by Fraser Harris

There is a great deal of information about mining for gold in Montana from the Bureau of Mines and Geology located at Montana Tech in Butte, Montana. The state is one of the signatories to the Mining act of 1872 that recognizes the right to file a claim on public lands belonging to either the state or federal government.

Western Montana is divided into two sections the Northwest and the Southwest in the northwest part of the state gold is found mainly in recent glacial moraines. During the early days when gold was selling for $20 per ounce of gold deposits found here were not considered to be economic although it was always possible to find gold. With today's prices the gold in these glacial moraines may become economically viable at $1500 per ounce.

The Berkley Pit in Butte Montana an abandoned copper mine where gold was produced as a byproduct.
Photo by Cybergrl

Most of the gold in this thing however is found in the southwestern part of the state where many of the rocks are of Archean age is similar to those in the Abitibi region of Canada were mostly gold was laid down between 2.8 and 2.6 billion years ago.

Some of the greatest mines in the United States are located in western Montana there were copper mines many of them produced gold as a byproduct from refining copper. The greatest of these copper mines was the Anaconda Mine located near the city of Anaconda. This mine was discovered right after the Civil War by an Irish prospector that was looking for gold, and found copper instead.
The Anaconda mine was actually named because of a newspaper headline the Irishman saw while he was serving in the Union Army near the end of the Civil War. The headline read, “Grant encircles Richmond like a giant Anaconda.” Both the mine and the city were named after this giant snake found in the Amazon basin.

Gold is found throughout Western Montana wherever there are mountains. The best place to look for placer gold is in the rivers and streams draining those mountains. According to one source is doubtful that the old time prospectors ever found all the gold that is deposited there. There are now many prospecting tools that were unavailable to the early prospectors, one of the most useful of these is the metal detector.

The metal detector that is capable of detecting gold in hard rock or placer deposits. The best tool for finding gold is one that the old time prospectors were very familiar with it is the gold pan. To this day no one has ever devised a better the way of discovering gold deposits.

Aside from gold prospecting Montana also affords the prospector the chance to find sapphires along the Missouri River. There are many areas along this river that are open to fee prospecting. In addition there are several other localities in the state where you can find various gemstones for a fee.

Wednesday, April 20, 2011

Gold Goes above $1500 per Ounce


Gold Rises Above $1,500 to Record on Weaker Dollar, Inflation Fears

Wednesday, 20 Apr 2011 10:45 AM

Read more: Gold Rises Above $1,500 to Record on Weaker Dollar, Inflation Fears 

Gold Occurrences in South Dakota

Before it closed in 2002 the Homestake Mine in Lead, South Dakota was the deepest gold mine in North America. It had operated almost continuously since 1874 where the gold was found in association with cummingtonite schist. The depressed price of gold at the time the mine was closed in 2002. The mine has been since converted by the National Science Foundation into an underground laboratory devoted to the search for neutrinos and other subatomic particles from space.

Until the recent discoveries of large gold deposits in the Carolinas and Georgia South Dakota had the distinction of being the eastern most state that was a large producer of gold. It also has the distinction of having a war between the Indians and Whites over the gold deposits in the Black Hills, an area that was considered sacred by the Sioux. This led to the Battle of Little Bighorn in eastern Montana where the 7th Cavalry under George Armstrong Custer was virtually wiped out by the Sioux warriors.

Airforce One flying over Mt. Rushmore in the Black Hills of South Dakota

Within a year of the Battle of Little Bighorn the Black Hills were swarmed with thousands of gold seekers. Although gold was known to occur in the Black Hills it was not a safe place for white men to venture because it was considered as sacred ground by the Sioux. The gold discoveries came fast and furious until he finally culminated in the discovery of the Homestake mine in 1876.

During the early days of the gold rush in the Black Hills mostly action was centered around Deadwood where the famous Western gunfighter Wild Bill Hickok was gunned down while playing poker holding the dead men hand of aces and eights.  It wasn't too long before gold was discovered on the other side of the mountain in Lead that was developed into the Homestake mine. The mine is now owned by Barringer Gold and they have not decided to reopen gold-mining here, but there were plenty of other gold mines in the Black Hills that over the years also produced gold.

Crystalline Gold from South Dakota

There are still plenty of opportunities for small-scale miners in the Black Hills, but you have to keep in mind that the early prospectors were pretty thorough in their search for gold. What they lacked were some of the modern devices for finding gold that we now have. These new devices make it possible to find gold that the old-time prospectors missed. Placer gold can be found in many of the rivers and streams of the Black Hills as well as rivers that lead out of the Black Hills.

Another place where metal detector comes in handy is prospecting in rivers and creeks. Every year more gold is eroded from the banks of creeks that finds its way into the water courses. This does not mean that you shouldn’t overlook the use of more conventional tools like gold panning kits and dredges for mining placer gold.
The other gold that is present here is what is termed lode gold that is found throughout the bedrock of the central Black Hills. This is an area of pre-Cambrian rock that was thrust up through the sedimentary rocks that surround it by earth actions in four different geologic episodes in the past.
Erosion from the rocks of the Black Hills has reached as far east as Minnesota in the form of a conglomerate. Gold is often associated with conglomerates as fossilized placer deposits. The conglomerates east of the Black Hills may prove to be another area containing gold. The largest gold mining district in the world is the Witwatersrand in South Africa that has produced more gold than all the other mining districts in the world combined is also hosted by an ancient deposit of conglomerate.

Tuesday, April 19, 2011

Gold Nugget forming Bacteria

During the late 1970s and new theory was put forward about the formation of gold nuggets with this theory stated that they were formed by a pair of bacterium; one of these was named Cupriavidus metallidurans and the other was named Delftia acidovorans either of which was capable of fixing gold from a solution of gold tetrachloride that is a compound that is highly toxic to ordinary bacteria.

Bacteria under an electron microscope NASA

Cupriavidus metallidurans and a similar bacterium Delftia acidovorans have the ability of precipitating gold from a solution of this chemical.  The gold often aggregates as a nugget that is made from their waste products. No wonder the Aztecs used to call gold the excrement of the gods.

It is a well-known fact that there are some bacterium that get their endorsement from metals the most common is the iron fixing bacteria that produce bog iron ore or form a thin film on the surface of swampy areas that looks like an oil slick, but when you touch the film it breaks up into a rectangle shaped fragments. There are some metal fixing bacterium that are being used today for remediating contaminated industrial Sites. There are specific bacterium for all the heavy metals including one for copper that is now being used to produce about 25% of the copper being mined in the world using the heap leach process.

The large Mojave nugget weighing 156 ounces that may have been formed by bacterial action.
Photo by Chris Ralph 

There is an Australian geologist claims he is found some convincing evidence of gold fixing bacteria colonies that are in better then gold nuggets. He is further convinced that he is seeing these bacteria structures under an electron microscope that were not the result of anything he did.

A geologist with the United States Geological Survey first postulated this idea in the 1970s, but he later claimed that many of the structures he saw were from his washing the gold samples with an acid solution before he observed them under an electron microscope.

It hasn't reached the proportions of a cottage industry yet although for many years it was felt that gold feeding bacteria in rivers and streams that fixed the gold ions in the water creating gold nuggets. To our knowledge there have been no enterprising souls that are they lately to start doing this yet although if it is true there are probably more than one that is at least thinking.

Monday, April 18, 2011

Nancy Twinkie sees Green and finds Platinum

After a few prospecting and rock hounding trips it was apparent that Nancy Twinkie was going to become a seasoned prospector and it wasn't just for gold. On the road from Chester Massachusetts to Middlefield you drive by a long stretch of serpentinite along the road where the builders had blasted the road out of the side of a mountain. The serpentine that came off that mountain during the 19th century was used as ship’s ballast by an enterprising ship captain that originally came from Chester.

This is a piece of uncut jade that resembles the serpentine found in Chester, Massachusetts.

In a previous voyage he had taken some of the serpentine to China, and the Chinese jade carvers fell in love with the stuff because it looked just like jade and was easier to car because it was softer. For it while there was a brisk trade in the serpentine, and several shiploads found their way to China where it was carved then exported back to the United States and the rest of the Western world as Soochow jade.

Just about in the center of this exposure of serpentine a small stream came down off the mountain, and although at different times I had stopped alongside this road cut to pick up some samples of serpentine myself, and quickly discovered that it was fine cutting material for making cabochons that were greenish incolor and displayed some interesting patterns.

A platinum nugget of the same color of what we found in our gold pans.
Photo by Rob Lavinsky

On one of our rock hounding trips into the Berkshires Nancy Twinkie and me stopped at this small stream to see if it contained any gold. Because serpentine is derived from metamorphosed oceanic crust that in some places is called greenstone there was a pretty good probability that we may find some gold. We didn't, but what we did find were some very small flakes of silvery metal that although we never tested these flakes to see what they really were there is a good possibility that they were platinum. Serpentine is what they call an ultra-mafic rock in which platinum is known to occur; so there is a good possibility that was what we found that day.

Gold associated with belts and greenstone in many places in the world where they produce gold; one of these so called greenstone belts is the Abitibi gold belt in Québec and Ontario is one of the great gold producing areas on earth. You might say that Nancy Twinkie saw the greenstone, serpentine, and probably found platinum.

Detrital Gold Deposits

Maybe you have heard of the Witwatersrand in South Africa if you haven't yet is the world's largest deposits of gold that since its discovery in 1886 has produced over 40% of the total gold supply ever mined in the world. This makes it the most glaring example of a detrital gold deposit in the world. The type of rock hosting this vast deposit is conglomerate that until about a year ago the source of its gold was unknown. By working with an isotope of iridium a team of geologists was able to pinpoint the source of this gold In eroded highlands delayed to the north.

Conglomerate the gold in this rock is usually found in the cement holding the pebbles together.
Photo by Hannes Grobe

The Witwatersrand is not the only deposit of conglomerate in the world that contains gold. In the area around Timmins Ontario there are also mines that produce gold from ancient conglomerates of Archean age between 2.8 M2 .6 billion years old. It is not only gold that these ancient conglomerates are apt to contain a common Association in rocks of this type are uranium mineralization. This is been taken advantage of at Elliot Lake, Ontario where some of the largest uranium mines in the world are found. The same deposits also contain significant amounts of rare earth elements to the point that the mining company Pele Mountain Resources (TSX-V ~ GEM) headquartered in Toronto, Ontario. At their Eco Ridge Mine in Elliot Lake, Ontario they are actively searching for both uranium minerals and rare earth minerals. The conglomerate at the Eco Ridge Mine also contains some gold.

Sandstone in a red bed that has been cemented and stained by iron oxide.
Photo by Anne Burgess

Ancient conglomerates are not the only place where gold can be found in sedimentary rocks as detrital gold is also found in many types of sandstone as small grains, and can even be found in fine-grained shale as microscopic particles that are too small to be seen with the naked eye. This kind of gold was never recovered until recently when Newmont Mining developed the gold deposits of the Carlin Trend in northern Nevada.

A closeup of the Marcellus Shale found in the eastern United States.  Aside from holding a vast amount of natural gas the Marcellus Shale sometimes contains gold in very fine specs that are invisible to the naked eye.
Photo by Lvklock

Most of those miners that are working with placer gold deposits in the rivers and streams of the world or along the beaches are also dealing with a type of detrital gold deposit in the form of specs of gold to have been eroded from hard rock and have been swept down river by the action of running water to where we can find them in the gravel deposits of the stream bed.

Conglomerate is nothing other than stream gravel that has become fossilized over time; just about any time you find conglomerate when you are prospecting it is a good idea to have a very careful look at the deposit. This also applies to sandstone and shale since they are also sedimentary rocks that have been produced by the action of running water.