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Monday, July 30, 2012

Tales of the Devil to Date

The new entrance to Mine #1 The shaft is 40 feet deep with an adit going off from the bottom northweat for 10 feet that is 6 feet wide and 7 feet high.  The adit is well timbered and the shaft was filled with debris dating back to the 19th Century.
Photo by John Carter

We have rediscovered an old mining complex in western Connecticut that to date comprises two mine shafts with accompanying adits.  The first mine consists of a shaft approximately forty feet deep with an adit going off to the northwest that is ten feet long, six feet wide and sever feet high.  Town records reveal the first mine was a prospect hole that may have been created in pre-Revolutionary days; the second mine was just discovered on July 30, 2012 and is yet to be explored.  Town records indicate this mine may have an adit up to 140 feet long.

At the end of May 2012 a blue ribbon committee was convened at the site consisting of Charles Merguerian of Hofstra University, Nicholas Bellantoni of Uconn, Stefan Nicholescue of Yale, John Carter of Geotek and two engineers, none of us could determine what they were mining.  The town P&Z Officer finally discovered some old records that divulged the fact the second mine was dated to 1858.  The mineral mined was chalcocite an ore of copper.

The mines were found within two miles of Cameron’s Line a major fault system that extends from Staten Island, NY the western mountains of Norway under a series of different names.  There are several important mines located in the proximity of this suture zone producing gold, silver and copper.  The largest copper mine in the U.S. before the discovery of copper in the Keweenah Peninsula of Michigan was the Argo Mine in Vermont that is also associated with this large fault system.

The property where these mines are located is highly mineralized containing in addition to chalcocite, malachite, pyrites, quartz, kyanite, ilmenite, magnetite, cerrussite, beryl and many other minerals yet to be identified.  Although there are no plans to resume mining operations at these old mines mineral specimens will be available for sale.  For further information contact John Carter at or 860-469-4804.

Many of the specimens of kyanite, ilmenite and magnetite are of museum quality and are really spectacular.  Some of these specimens are on display at the Yale Peabody Museum in New Haven, CT.

Friday, July 13, 2012

The Geology of Gulag Gold

Gold mining prisoners in the Kolyma Basin.  They are mining placer gold that is found throughout the area.

The Gulag Ore Field or more correctly the Ducat gold/silver deposit that is located in the central part of the Balygychan-Sugoi trough that is a graben shaped depression that is located near the town of Omsukchan, Kolyma that adjoins to its north the Okhotsk – Chukota a marginal continental volcanic belt.

The deposits of gold are centered on a Cretaceous (ca. 120 million year old) volcanic dome consisting of ultra-potassic rhyolites, ignimbrites and tuff that are interlayered with black argillites.  The whole volcanic complex is intruded at depth by a late Cretaceous (ca. 85 million year old) granite that is from 1,200 – 1,300 meters below the surface.

More gold miners at work in the Kolyma Basin

There were pulses of igneous activity that caused hydrothermal activity to occur in the dome that involved large quantities of fractured, porous and highly permeable Cretaceous rhyolite sills and other steeply dipping subvolcanic bodies to be affected covering an area that covered more then 25 square kilometers.

Most of the known mineralization was later to the younger intrusion that includes tin bearing greisen-type that occurs in the contact zones of the granitic plutons. They ore deposits himself were located at a considerable distance from the granite.

Part of the Kolyma Basin is within the Arctic Circle giving it a sub-Arctic climate having very cold winters that can last for up to six months. Most of the area is covered with permafrost and tundra. During the winter temperatures range from -19°C to -38°C with even lower temperatures found in the interior. Besides gold there are also rich reserves of silver, 10, tungsten, mercury, antimony, coal, oil and peat. It has been estimated that the area contains in addition to gold 1.2 billion tons of oil and one point 5,000,000,000 m³ of gas.

This is the area whose mineral wealth was discovered by Yuri Bilibin in the 1920s that was quickly developed into the infamous Gulag prison camps by Stalin in the 1930s. There was also the area Bilibin used as the model for his theory of Metallogeny and Global Tectonics that has gained much traction sense of the world of geology.

Development began in 1932 and of Joseph Stalin the Kolyma Basin became the most notorious place for the Gulag labor camps. It has been estimated that over 1 million people died en route to the area or in the Kolyma’s between from 1932 until 1954. It was Kolyma’s reputation that caused Aleksandr Solzhenitsyn ferrite his famous book the Gulag Archipelago. In this book Solzhenitsyn came to characterize it as the “pole cold and cruelty.”

Gold and platinum were found in the Kolyma during the time when industrialization began in the USSR under Stalin’s First Five Year Plan in a period when the need for capital that would finance this economic development.  The Kolyma Basin gold was a perfect fit and development of the basin began in 1932 based on prisoner labor. 

In 1932 construction began on Kolyma Highway into the interior those that become known as the Road of Bones because of the number of people in Paris in its construction. This role eventually came to serve 80 different camps that were not have around the region of the uninhabited taiga. The first director of the Kolyma camps was Eduard Berzin who was the Cheka officer that was removed in 1937 and shot during the period of great purges of the USSR.

Far Eastern Russia geologically is North American plate that also includes Kamchatka Peninsula in northern Hokkaido Island of Japan. This being so it is probable that the gold deposits of this part of Siberia are closely related to those found in the Tintina gold belt of Alaska. It also indicates that most landmasses on Earth are really just one supercontinent with the sole exception being Antarctica.

Tuesday, July 10, 2012

Tales of the Devil: The Hammer of Thor

The new find on the site

Somebody asked me why we named this series, Tales of the Devil. Well back in 1819 one of the sources wrote in the American Journal of Science 1st Edition a paper about minerals found in Litchfield County.  Then he got religion and during the 1850’s wrote a tract called “Tales of the Devil.”  By then he must have been a full-fledged geologist from Yale.  At least he knew his subject matter.  However, “Tales of the Devil” fits this place as well as any other story, but finally some old records came to light that explained the whole place.

Since its rediscovery in March 2012 this site has had at least five PhDs tugging their forelocks trying to figure out what in blue blazes went on there.  Finally one of them found a collection of old records that explained the whole deal and even named some of the historical personages that were involved with the site including P.T. Barnum and Thomas Edison.

The first shaft and adit that was discovered was apparently a prospecting pit, or if you prefer a gopher hole. This consisted of the mineshaft that was 40 feet deep with an adit at its bottom going off that was 10 feet deep by 6 feet wide by 7 feet tall. It is apparent from the records that this may have existed since pre-Revolutionary War times. Most of the mining occurred in the mid-19th century and according to the records underground mining in the location included an adit that was more than 140 feet long.

Because of the geology on the site being similar to those where gold was found we assumed that was what they were looking for, and probably was. According to the old records covering the site what they were actually found was copper, and it was in the form of the copper sulfide mineral called chalcocite, a grey colored mineral.

Actually this tale doesn’t have anything to do with Thor except there’s a Norwegian involved in its telling. He was one of the PhD's.  Another one came from Transylvania.

Monday, July 9, 2012

The Upside Down Mine

Sterling Hill Mine in Ogdensburg, New Jersey
Photo by Dmadeo

No, this isn't about a gold mine it's about a zinc mine specifically the one at Sterling Hill, New Jersey that for many years produced zinc and was one of the largest mines and the East Coast of the United States. The ore produced from this mine is noted worldwide for its many fluorescent minerals, but like all mines in eventually came to it in and was closed down although it still operates as a museum. At this mine and the ones in nearby Franklin, New Jersey form a canoe shaped orebody hosted in marble that is been the subject of much controversy over the years as to its origins.

During the 1960s Brian Skinner of Yale University was working for the USGS and with a colleague started speculating on how this ore body was emplaced. Under normal circumstances it is assumed that the ore came from deeper down in the bowels of the earth. However in this case under the marble was a layer of impervious rock that apparently did not allow the ore bearing hydrothermal fluids to rise up from below the marble.

Willemite, Franklinite and Rhodocrosite under Ultra-violet light from Sterling Hill
Photo by Rob Lavinsky

Skinner and his colleague were working in the mine one night when the question of the deposit’s origin came up.  The layer below the marble was impervious, but the marble itself wasn’t.  Many layers of sediments were deposited above the marble including some that were volcano-clastic in nature.  These rocks were also pervious allowing ground water to perk down from higher up that were capable of bearing ore bearing fluids.  They came to the conclusion that the ore bearing fluids came down from above and perked through the marble until they hit an impervious layer below the marble.  Here the ore bearing fluids stopped and gave up their load of dissolved minerals creating the deposit. However there is zinc minerals dispersed throughout the marble above the actual deposits.

This is all theoretical, but there are other examples of this same mechanism at work.  One glaring example can be found in the iron deposits found in northwestern Connecticut.  For almost two centuries the iron mines in Salisbury yielded some of the richest iron ore on earth that had its origin in the overlaying Walloomsac formation of schist interbedded   with marble.

The same specimen as above under normal light
Photo by Rob Lavinsky

The origin of this formation is volcano-clastics that came from an island arc that formed off the then east coast of North America that collided with the continent during the late Ordovician and caused the Taconic Orogeny.  This volcano-clastic material was the source of the iron that formed the famous Salisbury iron deposits, and supplied the magnesium that turned the limestone into dolomite.  The Walloomsac formation extends south from Lake Champlain to Manhattan where it underlies among other things the New York Stock Exchange.  Throughout its length at its base and in the underlying marble iron deposits are sprinkled like plums in a plum pudding.

It is theoretically possible that some gold deposits that are hosted by marble were deposited by the same mechanism i.e. leached from the overlying deposits.  A possible example of this mechanism in action are the gold deposits of the Carlin Trend in Nevada.  Another suspect is the San Pedro mine in San Luis Potasi, Mexico.  Both of these deposits are hosted in marble.  Keeping this mechanism in mind might lead to the discovery of other deposits of valuable metals.

Sunday, July 8, 2012

Streak Plates for Mineral Identification

Black and white streak plates showing colored streaks for pyrite and rhodocrosite on black & white streak plates

One of the most important tools in the arsenal used for mineral identification is the streak plate.  This aid to mineral identification is usually a piece of unglazed porcelain. The two colors most commonly used are black and white with white used for dark colored minerals, and black used for light colored minerals.

Black colored stones are often called touchstones for testing gold that leaves a golden colored streak that when treated with nitric acid can be used to tell the karat of the gold being tested.  If you draw a line with gold on a black piece of unglazed porcelain it leaves a golden streak that can be tested by applying different concentrations of nitric acid to the streak thereby finding its karat or quality.  24 karat gold is unaffected by the acid, but as the amount of gold in a sample decreases you are able to determine how much gold there actually is in the sample.  Different karat values have different colors.  For ages this was the definitive test for gold but it has been replaces by more accurate tests based on electronics.  In the test 24 karat gold is unaffected, but lesser grades of gold show increased chemical activity.

The black streak plate is used for testing for other precious metals belonging to the platinum group metals (PGM).  In most cases it is used to test light colored minerals.  Conversely the white colored streak plate is used for testing light colored minerals.

For our prospecting and mineral collector friends we have made available a streak testing kit composed of one each black and white 2”x 2” test plates for $10.95

Individual streak plates are available for $5.75 each.

They can be ordered online with instructions for their use included.

Full set black and white: $10.95 

Streak Plate Set (B and W)

Single black streak plate $5.75: 

Black Streak Plate

Single white streak plate $5.75: 

White Streak Plate

Connecticut residents please add 6.35% sales tax.

Shipping is included on all orders.

From time to time we will be adding other items useful for the mineral collector or prospector.

Photo by Ra'ike

Thursday, July 5, 2012

Gold Deposits in Ancient Turbidites

The southeastern coast of the United States - NOAA

The largest deposits of gold on Earth are found in ancient turbidites that include the Witwatersrand of South Africa and the Abitibi found in Canada in both Qu├ębec and Ontario. By definition a Turbidite is a landslide that occurs on a continental slope of a continental landmass where the erosion products of the continent eventually work their way to the abyssal plain at the bottom of the ocean that can be several kilometers deep.

Turbidites start at the edge of the continental shelf and can be caused by several different geological phenomena. They are deposited by a special type of water flow called a Turbidity Current that can be started by an earthquake, a powerful oceanic storm or in some cases just by the amount of material that collapses in on itself. The turbidity current contains not only water but suspended debris that causes it to flow out of town little slow but a speed that exceeds that of water itself because the current is also carrying suspended particles. Depending on the height of the slope the speed that it flows can reach as much as 70 km/h.

Once this flow reaches the bottom of the slope it quickly loses its forward speed and as it does drops off particles according to their density. It has such a high specific gravity of more than 19 gold is one of the first things that is dropped from a turbidity current. The finer particles and spread out over the abyssal plain of the ocean extending across the abyssal plain for hundreds of kilometers. In many cases at the edge of the flow the finer particles may only be a few millimeters thick, but over time this can actually be built into deposits of great thickness.

Mostly gold of the Turbidite deposit will say relatively close to the edge of the continent. Examples of these Turbidite flows are found in several places in the world one of the classic examples is the MegumaTerrane of Nova Scotia.

Some of the metals found in this environment include gold, silver, tungsten and antimony.  In western Connecticut the Rowe schist is an example of a metamorphosed turbidite.  This formation extends from northern Massachusetts almost to Long Island Sound in Connecticut.  Over the years reports of gold have been rumored about with this formation, but what is lacking is substantial proof i.e. no core drilling.

A capsule description of a turbidite deposit is gold-quartz veins, segregations, lodes, sheeted zones that are hosted by fractures, faults, openings in anticlines, synclines, along bedding planes in the turbidites and those that are associated with poorly sorted clastic sedimentary rocks.

These rocks are typically found close to the margins of continents or in back arc basins.  These rocks were typically deposited in submarine troughs, periarc basins, foreland basins and other remnant oceanic basins.  One feature that is typical of these rocks is multiple deformation events accompanied by metamorphism.  They show evidence of being thick sediment sequences displaying both deformation and are metamorphosed.  Although there can be some igneous rocks found in one of these deposits they tend to be quite rare and are usually present as pegmatites.  In some cases there are younger granitic intrusions associated with these rocks raising them to be raised to greenschist, but in some cases can reach amphibolite grade metamorphism.

The ore mineralogy of one of these deposits whether it is principle or subordinate includes native gold, pyrite, arsenopyrite, phyrottite, chalcopyrite, sphalerite, galena, molybdenite, bismuth, stilbite, bornite and other sulfosalt minerals. These minerals generally have a low sulfide content of less than 2.5%. The usual minerals found in association with these ore minerals are Quartz, carbonates, feldspar and chlorite.

When rocks of this type are discovered in glaciated terrains they may undergo deep weathering where alluvial recycling may produce rich placer deposits, such as in the Bendigo region of Australia.

There is several factors that control the ore deposits that are often found in fold crests, discordant veins and tension gashes. In some cases such as the in the Bendigo there is a relationship between ore deposits in the amount of graphite that is found in the country rock. The structural control is often extended to a district causing a scale alignment of deposits. Sometimes the veins appear confined to a specific stratigraphic interval that is often near to a change in stone type. Sometimes a more subtle relationship occurs lower deposits more closely related to the upper portion of the turbidite as of the magma district of Nova Scotia.

Because the low sulfide content, the majority of Quartz veins houses most geophysical methods of geophysical exploration to become ineffective it is often necessary to resort to the more usual prospecting techniques that are often accomplished with a gold pan by tracing the deposit.

In the deposit of this kind is not unusual to find deposits that range from a 50 g per tonne. Many of these are attractive targets for exploration as many of them are world class deposits.

Deposits of this type become incorporated into continental land masses with the death of an ocean by two continental masses colliding and the turbidite deposits are squished between the continents causing the turbidite to become incorporated into the mountain range that is a result of the collision. 

Tuesday, July 3, 2012

Gold Occurrences in Burkina Faso

Map of Burkina Faso  -  CIA

In the past 40 years there has been a great deal of interest in gold mining in Burkina Faso. This is a country that is very geologically rich with the Poura region alone accounting for over 25 tonnes gold. As of 2003 the government brought about a new Mining act and immediately after there were more than 30 companies that have undertaken exploration projects in the country. They also created five new mines that are on the point of full production.

As demonstrated by the Abitibi region of Canada some of the richest gold mines in the world are located on greenstone belts.  In Burkina Faso greenstone belts cover about 3,000,000 km² of West Africa the Burkina Faso accounted for approximately 21% of these greenstone exposures. There are about 13 international mining companies that are active in this area now. .

As many as 13 international mining companies are working in the country mainly in the Greenstone belts. These belts account for over 21% of West Africa's Greenstone belt exposures that house on the world's most prolific gold mines. Some of these mines are capable of producing over 100 thousand ounces of gold per year. Much of this gold is produced by the heap leaching process and probably accounts to more than 1,000,000 ounces per year. Although some of these are producing mines, more of them are exploration projects that have been ongoing for some time.

All of the United Nations development program and Burkina Faso indicates that the early Proterozoic (Birrimian) Greenstone belts located at Boromo and Hound consists of steeply dipping volcanic and volcano-sedimentary units that have been intruded by the Eburnean granitoids there about 2 billion years old that have undergone incipient to low grade greenschist metamorphism. Many of the former gold prospects and mines are found in the Greenstone belts including the spell Poura vein gold deposit and the Dossi shear zone prospects. Much of gold that is discovered is associated with scheelite, calcium tungstate that is an ore for the metal tungsten.

Gold mining is one of the newest stories in Burkina Faso in recent years where the gold mining industry has been developing apparently inexhaustible resources.  There are many Australian companies that are already there searching for gold.  Many are finding it.

Most of the primary gold deposits are derived from metamorphic rocks that were developed from auriferous rocks that were eroded away long before the placer deposits bearing them were metamorphosed in the older volcanic and volcano=sedimentary rocks.  In this they are similar to the rocks found in the Witwatersrand district of South Africa and the Abitibi greenstone belts of Canada.