Introduction
For the last 20 years, the author has been visiting mines, mineral fairs, and mineral dealers to purchase and self collect minerals from over 40 countries to date.
One of his guiding inspirations was Peter Bancroft's excellent book Gem and Crystal Treasures which describes Bancroft's selection of the 100 localities for the worlds best mineral specimens.
This essay will describe some of the background and history of famous localities, and the minerals found there.
It is anticipated that those readers interested in the Precious Metals, Gold and Silver, and the PM share market, may find interest in these anecdotal tales of mines and minerals, and enjoy the beauty of one of nature's hidden treasures; --- mineral specimens. ---
Note: Gold and Silver are metallic elements. They are also minerals when they occur in pure form in nature, and are then described as native gold and native silver.
There are just over 4000 mineral species discovered world wide to date.
Incidentally, new minerals are still being discovered today thanks to the advance of science in laboratory analytical techniques, rather than new mining or exploration technology.
Minerals tend to be named after localities, new specimen discoverers, famous geologists, mineralogists, or collectors. Take for example Morganite, the Beryl variety coloured pink by traces of manganese. In the year 1911 New York gemstone expert G.F. Kunz suggested to give Pink Beryl the status and standing of an individual kind of gemstone, and it was named in honour of banker and minerals collector John Pierpont Morgan, thus receiving its current name: Morganite.
Mexico
Silver Sulphides - Acanthite, Stephanite, and the attractive, rare, and sought after, ruby silvers Polybasite, Pyrargyrite.
In 1998 the author spent 2 months touring the silver mines in the north of Mexico with the late Walt Bowser as guide. We drove down through Chihuahua, Fresnillo, Durango, Mapimi, Zacatecas, Guanajuato as far south as Taxco, (large market for silver artefacts), and then back to Texas.
This is desert country, and all that changes on the road south are the types of cactus, from Yucca to the Joshua tree, with other types remaining ubiquitous like the prickly pear, attractive when in flower. The Agave plant is the base for the notorious Tequila.
It is also Pancho Villa country, a controversial revolutionary, folks hero or bandit, who robbed the silver trains from the mines on occasion in the early 20th century.
"Senor Walt" was also received in the mining villages as a hero during our visits, because he distributed second hand clothes, shoes, and other items to the poor mining families, meanwhile filling up his trailer with the mineral specimens we bought from the miners.
In Zacatecas we descended the mineshaft to the 100 level at the Veta Grande mine.
Here Walt tells the full story of a 1997 tour for those interested in all the mineral details, courtesy of the Canadian RockHound web site.
Very sadly Walt passed away in 2003, but he was such a legendary charismatic character that 20 or so of his friends and family including myself got together by email and wrote tributes to him. The results were collated and published in a special commemorative pamphlet edition of Rockhound Notes in June 2003. This was a most moving experience and a novel spontaneous expression of Cyber-grief.
A highlight of the tour was the visit to the famous cave of swords with its massive gypsum crystals up to 2 metres in length seen here with a photo of the author.
Some photos of Mexico mineral specimens from mineral dealers can be seen at the following web sites; http://mineral.galleries.com/minerals/fablocal/mexico.htmJohnBetts, Arkenstone selection, and http://www.davebunkminerals.com/ag/silver2.htm with the latter showing 3 pages of the above-mentioned silver sulphides from the mines in the areas visited by the author.
Native silver specimens are also occasionally found at some of the mines, such as at Batopilas, and the silver is usually in complex forms often described as and resembling wire.
Some of the silver mines in Mexico have been operating for over 400 years, and are so rich in silver ore that it is estimated that up to one third of all the silver ever mined in history came from this region. Compare this to average mine lives worldwide usually measured in years or decades, not centuries. Silver is normally mined as a by-product in lead/zinc mines, but in Mexico the ore often consists of a high grade mixture of the silver sulphides described above.
The famous Roebling suspension bridge, 325 metres long, crosses a deep canyon at the Ojuela mine near Mapimi, and remains as a landmark at a mine that still delivers rare and world-class specimens, including Legrandite, and has produced some of the worlds best Adamite specimens. The bridge, the second longest suspension bridge in the world when constructed in 1899, connected the mine with the new town and railway. Penoles operated the mine from 1893 until its closure in 1946. "Thousands of Penoles miners and a million Tonnes of high grade silver ore passed over the bridge," (Bancroft).
The houses that once housed 2000 miners (click here and compare with my photo in 1998!!) are now ruins, and the mine deserted apart from a few visitors like myself.
Mexican Opal: At Queretaro, the author visited a fire opal mine and after purchasing a mine run lot, was invited by the owner to self collect some material in the "open pit" mine.
Specimen Mining
Commercial mines target production volumes, and any extraction of mineral specimens has to be carefully managed to avoid disruption to mining schedules.
However a new type of mining solely for mineral specimens for sale to collectors and museums has emerged over the last decade or so. Bryan Lees of Collectors Edge has pioneered new techniques for working disused commercial mines, or other mineral localities to extract mineral specimens undamaged by the mining processes.
His most noted success has been at the Sweet Home mine, Alma Colorado, which the author visited in 1995. The Sweet Home was originally a silver mine, but is now famous for the world's best Rhodochrosite specimens.
- Gold -
Gold is a noble and versatile metal as seen by its properties.
It is also rare, gold (Au) is only 0.002 parts per million of the earths crust, compared to iron (Fe) which is 62,200 ppm. Note that gold is more rare by a factor of 40 than silver (Ag) whose abundance is 0.08 ppm.
However gold specimens are even more rare. This is because in the majority of gold mines, the gold is not visible to the naked eye, but finely dispersed in the matrix, which may consist of quartz, sulphides, or other host rocks.
Note how gold specimens here from different mines have subtle differences in appearances, occasionally allowing identification of the source mine.
Gold was featured at this years Tucson Mineral Show 2004, the world's largest mineral fair held annually at Tucson, Arizona. Scroll down here courtesy of Trinity Mineral for some more wonderful photos of gold in various shapes, forms, and sizes, including some world-class specimens from localities described below.
Eagles Nest mine, California: Some of the most attractive native gold specimens in fine crystallised form have come from this mine, and have been marketed by Wayne Leicht. Currently this specimen mine operation has started up again and it is hoped good material will soon be on the market again in reasonable quantity.
Crystalline native gold on quartz matrix. Eagles Nest Mine, California, USA. 8 x 7 cm. Museum of Geology, Lausanne, Switzerland. Photo Stefan Ansermet.
Breckenridge, Colorado was settled in 1859 as a gold and silver mining town. A collection of the distinctive gold specimens mined over the years can now be seen at the Denver museum, including Tom's Baby, an eight-pound nugget of crystallized gold unearthed in Breckenridge in 1887.
Gold specimens in nugget form are also collector's favourites, and are often found in alluvial gold fields using metal detectors.
Gold, as a noble metal, is relatively chemically inactive. However it does occur rarely in nature in the form of minerals, combined with other elements such as silver, copper, tellurium, lead, and antinomy.
Cripple Creek, Colorado is another famous gold mining district, where gold was found in the form of Tellurides. Here the author went on an underground tour at the Mollie Kathleen gold mine.
Exploration and discovery of gold in the 19 th century was a chance affair and usually relied on finding visual gold, either in matrix in an outcrop, or in nugget form, or by gold panning in streams and rivers. Any rich discovery was often followed by a gold rush.
South Africa: The first gold rush started at Pilgrims Rest, which was declared a gold field in 1873; soon after digger Alec "Wheelbarrow" Patterson had found gold deposits in Pilgrim's Creek. The Valley proved to be rich in gold and by the end of the year, there were about 1500 diggers working in the area, living in tents in squalid conditions. (His nickname arose from the fact that he arrived at Pilgrims Creek with all his worldly possessions carried in a wheelbarrow.) President Burgers, on hearing of the gold strike, hastily had the Transvaal Mining Laws drafted, (none having existed until then), after a quick study of the Mining Laws of Australia, New Zealand, and California. He then visited the mining camp with some aides, and after some negotiations with the miners and amendments, the new laws were put into place.
Access in those days was via Mozambique crossing what is now the Kruger Park. A visit to the cemetery testifies to the low life expectation of the miners. Many, who escaped the dangers of lions and other predators succumbed to malaria or other tropical diseases.
In 2001 the author panned gold during a visit to Pilgrims Rest, and was delighted to see a few tiny flakes at the bottom of the pan, nestling with some other black heavy minerals. This photo shows the author inspecting some antique mining equipment at Pilgrims Rest.
South Africa still claims to be the largest gold producer, with ca 40% of the worlds known reserves, and some of the richest and deepest gold mines.
North America has experienced many gold rushes, including California from 1848 to 1864, and the Klondike in 1896 but at Nome the gold was literally found on the beach. "The coast was icebound for the season, but gold seekers began descending on the tent town in the spring of 1899. During that summer alone, more than two million dollars' worth of gold was taken from the beaches of the booming city of Nome."
It is interesting to note that, despite the short duration of these historical gold rushes, several new gold mines are planned to open in Alaska and British Columbia over the next few years.
Despite the large quantities of gold mined during these gold rushes, few specimens from that era remain. In fact the majority of gold specimens in collections today, have been mined in the last 25 years, either in specimen mines, or commercial mines with a policy of saving mineral specimens, and in smaller quantities from amateur gold panning and metal detecting.
It is to be hoped that new gold specimens for the collectors market will become available from some of these new mining projects.
This essay makes no attempt to cover all the best localities, (historically or more recent), for gold specimens, but for those interested in an in-depth coverage Robert B. Cook's article in Rocks & Minerals Jan/Feb 2004 is highly recommended. (see link in Further Reading below)
Gold exploration has changed radically from those bygone days. Geophysical and geochemical surveys are now used to identify drill targets. Drill programs are used to create Feasibility Studies, followed by permitting, construction and production, normally a 7 year process. The cost of building a new large gold mine runs into several hundred million us$.
The days of the Gold Rushes have gone, but Gold fever is now still occasionally seen on the stock markets, when gold drilling results are reported by a mining or exploration company!
One famous mine currently producing gold specimens for collectors is the Red lake mine.
David Joyce sells the specimens on behalf of Goldcorp, and kindly agreed for his essay to be reproduced here (an abridged version of the original which appeared in Rocks and Minerals).
The Red Lake Mine: The Richest Gold Mine in the World
David K. Joyce
Box 95551, Newmarket, Ontario
Canada L3Y 8J8
dkjoyce@attcanada.ca
Stephen McGibbon
Manager Exploration, Goldcorp Inc.
Balmertown, Ontario, Canada
smcgibbon@goldcorp.com
Introduction
In 1989, Goldcorp Inc. took over Dickenson Mines Ltd, a venerable gold mining company that, since 1948, had operated the Arthur White mine in the Red Lake mining camp, located north of Lake Superior, near the Ontario Manitoba border. Robert McEwen, chairman of Goldcorp Inc felt that the adage, "the best place to look for a new orebody is near an old mine" had some credence. Was he right!!? Goldcorp initiated an exploration program while the old mine rolled along as a break-even or money losing gold mining operation. During early 1995 while testing Goldcorp's geological theory, diamond drillers cut across a very high-grade body of mineralization that was soon to become the fabulous "High-Grade Zone (HGZ)". Diamond drilling continued and the HGZ has proven (at time of writing) to contain more than 1.96 million tons of high-grade ore containing 4.6 million ounces of gold. That is an average grade of 2.35 troy ounces per ton! Most gold mines in the world average well under 0.5 troy ounces per ton. So prolific was the change in fortunes of the mine, that the Arthur White mine was re-named the Red Lake mine.
There are other orebodies in the world that, being larger contain more troy ounces of gold. However, to our knowledge, there are no other gold mines that contain the average grade of ore that the Red Lake Mine does. These sorts of orebodies come along only once every several decades, or so.
The HGZ changed the economics of the old mine so much that Goldcorp Inc. decided to build a brand new mine around the new orebody in order to optimize its extraction. A new milling complex and offices were built along with a camp to house contract workers. The only significant parts of the original mine that remained in use were the headframe and shaft needed to access the orebody. Recently, however, Goldcorp has decided to also replace the old shaft and winze with a brand new 7,500 foot single lift, vertical shaft in an effort to speed up the mining of the new orebody and to improve the overall efficiency of the mine.
The impact of the discovery of the new orebody on Goldcorp, the Red Lake mine and the surrounding area have been dramatic. With millions of dollars surging into the local economy from the Red Lake Mine and the exploration efforts of other companies hoping to duplicate the feat, the Red Lake area has experienced a surge of prosperity and confidence not felt since the hey-days of gold mine discoveries in the 1940s and 1950s. Now, Goldcorp is cash rich with no debt, and is one of the most profitable mining companies in the world.
It became apparent early in the exploration of the orebody that visible native gold would often be encountered. The senior management of Goldorp decided, to their credit, that if specimen-grade native gold was encountered, some of it should be preserved as specimens to serve as a legacy of Goldcorp, the Red Lake mine and the fantastic orebody that produced them. David K. Joyce was retained to prepare specimens, on site and, then, to market and sell the specimens. Since production commenced, hundreds of beautiful, rich native gold specimens have been recovered and sold to museums, shareholders, collectors and universities around the world.
Many mines have zones of high-grade ore that are very profitable to mine. Few have had a zone like the High Grade Zone, however, which is still open at depth and, although smaller in width at depth, appears to be increasing in grade.
The property on which the Red Lake mine is located comprises fifty-eight patented mineral claims held by Goldcorp covering approximately 2,348 acres, which, on the west side, share a common boundary with Placer Dome Ltd.'s Campbell Mine. Goldcorp also holds mineral claims covering approximately 56,125 additional acres of prospective mineral ground in the Red Lake area. Access to the mine is by road and by air, with the closest major cities being Winnipeg Manitoba and Thunder Bay, Ontario.
The Red Lake mine is currently operating at a rate of 550 tons per day of ore. Mining is accomplished using, mostly, a mechanized cut and fill mining method utilizing jumbo drills and 5 cubic yard scoop trams. At the present time, ore is being mined between the 31 and 37 levels, at a depth of about 4,000 and 5,500 feet below surface. At the time of writing, ore averaging about 2.28 troy ounces of gold per ton is being hoisted to surface. When the new shaft is finished in 2006, production will increase to 1000 tons per day.
The mill at the Red Lake mine uses several techniques to separate gold from the waste rock. One circuit uses centrifugal force and gravity, employing Knelson concentrators and a Diester jig table, respectively to separate coarse gold from the rock. Another circuit employs flotation to float gold rich sulphides to produce a gold-rich sulphide concentrate. Third, a carbon-in-pulp circuit is used to capture the fine gold that is not tied up in sulphides. Much of the concentrates produced by the above methods contain bits of rock and other impurities. The concentrates are refined by smelting where they are melted and the impurities are removed as a slag. The finished products at the mine are dore bars, which are poured molten into molds, after the refining is complete. Dore is a mixture of gold and silver with some other minor impurities and, at the Red Lake mine, contain, on average, about 87 percent gold and 13 percent silver are poured on-site. The dore bars are sold to refineries who further purify the gold and sell it to end-users, financial institutions and investors. Goldcorp actually does not sell but retains a certain percentage of its gold, in the belief that gold is undervalued. Currently, Goldcorp owns more gold bullion than many governments of the world!
Security is very tight at the Red Lake Mine. All people and vehicles enter and leave the mine through a single gate. Security guards are diligent in searching all belongings and vehicles, to ensure that gold is not smuggled out of the mine. All people leaving the mine are required to undergo a search, similar to those undertaken at airports, with subjects selected at random. All briefcases and luggage leaving the mine are searched.
Regional Geology
Ontario and Quebec occupy much of the "Canadian Shield" a prolific, Precambrian age geological formation and the home of many of the world's greatest mines, past and present. There are many "belts" of greenstone (highly contorted, Pre-cambrian volcanics and sediments) throughout the Canadian Shield. These greenstone belts have been the geological environments where gold deposits are found such as: Campbell, Hollinger, Dome, Sigma, Kerr Addison, Lakeshore, Macassa, McIntyre, Hemlo, Doyon, Bousquet, Malartic, Camflo, etc., all multi-million ounce producers. Goldcorp's Red Lake mine lies in the eastern part of the Red Lake Greenstone Belt. This belt is made up of an assemblage of ultramafic, mafic and felsic volcanic rocks with a sedimentary sequence. These rocks are cut by a number of felsic and mafic dykes.
Styles of Gold Emplacement
The two major types of gold mineralization consist of high-grade quartz-carbonate-sulphide mineralization grading 2.35 troy ounces of gold per ton ("opt") and the lower grade sulphide zones grading 0.37 opt. To reflect that variation, the zones have been grouped into two categories, the high-grade zones (the "High-Grade Zone") and the sulphide zones (the "Sulphide Zone").
Mineralogy
Gold Gold is the principal ore mineral at the Red Lake mine and the mineral that is the most interesting to collectors. The gold in the High Grade Zone was largely emplaced as a result of gold-rich, siliceous replacement of carbonate veins and, as well, by injection into volcanic rocks. Large masses of native gold up to many hundreds of troy ounces have been encountered during mining. On occasion, knobs or masses of native gold can be seen protruding from stope backs or walls. These are rich sights to behold! It is from those places, that the most impressive specimens of native gold have been recovered.
There appears to have been some subsequent remobilization of native gold into fractures in quartz and carbonates (calcite, ferroan dolomite) and into intensely altered volcanics. Arguably, the best specimens of native gold result when the gold has formed as veinlets in these fractures. The gold forms more coherent, solid veinlets or "leaves"in the calcite and quartz than it does in the altered rocks. These veinlets, when exposed, become the "leaves" and "plates" that we see in the specimens from the Red Lake Mine. A large percentage of the native gold at the mine occurs only as fine fracture fillings or coarse masses in altered volcanic rock that are not suitable as specimens other than as examples of fantastic high grade ore!!
On occasion, masses of very coarse gold are encountered in dark gray-black quartz. This type of high-grade is slabbed and sold to lapidaries for use in jewellery. Geologists and others interested in ore textures find the slabbed high-grade specimens interesting, as well.
Berthierite and Stibnite The only other species that occur at the mine that are of interest to collectors are stibnite and berthierite. Rich, high grade-gold is, on occasion, associated with metallic black masses of coarse stibnite and berthierite. Crystals of these minerals have not been observed but their association with coarse gold makes for interesting specimens.
Specimen Recovery
This specimen from the Red Lake Mine shows a unique burst of native gold protruding from the top of the matrix of altered volcanic rock. 8.5 cm tall. D.K. Joyce specimen and photo.
Company geologists regularly visit stopes and development headings to gather samples and map local geology and to give direction to miners. The geologists are accustomed to seeing native gold in the HGZ but are constantly on the lookout for the extra-high-grade areas that are occasionally encountered. These extra-high-grade areas are erratically distributed throughout the mine and often run locally in the many hundreds of ounces per ton over distances of tens of feet. These super-rich zones are often the sources of specimen-grade-high-grade that can be prepared to produce the beautiful gold specimens for which the Red Lake Mine is becoming famous. When geologists encounter the super-high-grade areas, they collect any likely looking gold-bearing ore and place it in locked, metal boxes. These boxes are moved to the shaft, taken to surface and stored in the vault.
David K. Joyce, periodically visits the mine and works on each individual piece of high grade to, if possible, better expose the beautiful gold leaves, plates and other interesting formations that are enclosed in the matrix rock and vein material. He "reads" the grain of the rock and the directions of gold emplacement and then with a host of tools breaks, chips and chisels away the minerals that cover the gold, in an effort to produce aesthetic specimens that are coveted by collectors, investors and museums around the world. The vault can be a spectacular sight when full of native gold-bearing-hi-grade ore and finished specimens!
Interestingly, Goldcorp has retained one specimen in particular which consists of a thick vein of nearly solid gold traversing altered volcanic rock. The specimen is estimated to contain 298 troy ounces of gold! Goldcorp often brings this large specimen to trade shows to tantalize people.
Conclusions
The Red Lake Mine is, based on the very high average grade of current ore and life-of-mine ore reserves, to our knowledge, the richest gold mine in the world. To its credit, Goldcorp has decided to recover and market beautiful specimens of high grade ore to be sold to museums and collectors around the world, specimens that will serve as a legacy of this orebody. They will delight collectors, prospectors, museum visitors, and others in the future, as they all marvel at the occurrence of so much gold, in one place, at one time!
Acknowledgements
The authors would like to thank the management of Goldcorp for the opportunity to be involved with specimen recovery at the Red Lake mine, for permission to publish this article and for its foresight to save excellent gold specimens from the mine. The author would like to thank the following people for assisting or contributing to this article: Bruce Humphrey, chief operating officer; Chis Bradbrook, vice-president corporate Development; Gilles Filion, vice president exploration; Claude Lemasson, mine manager; Tim Twomey, senior geologist; Gabriela Sanchez, assistant to the chairman and Arlene Connolly, graphic artist. We would also like to thank Professor R. Cook for his invaluable review of the manuscript.
References:
MacGeehan, P. et Hodgson, C.J., 1982 Environments of gold mineralization in the Campbell Red Lake and Dickenson Mines, Red Lake District , Ontario in Geology of Canadian Gold Deposits, Canadian Institute of Mining and Metallurgy, Special Volume 24, 184-207.
Andrews, A.J. et Hugon, H. 1985. Alteration, metamorphism and structure associated with Archen volcanic-hosted gold deposits, Red Lake District; studies in the Campbell and A.W. White mines in Summary of field work and other activities 1985, Ontario Geological Survey. Miscellaneous paper no. 126, p 193-200.
Parker, J.R., Gold mineralization and wall rock alteration in the Red Lake greenstone belt: a regional perspective; in Summary of Field Work and other Activities, Ontario Geological Survey, Open File Report 6032, p. 22-1-22-28
Sanborn-Barrie, m. Skulski T., Parker, J., and Dube, B. Integrated regional analysis of the Red lake greenstone belt and its mineral deposits, western Superior Province, Ontario; in Current Research 2000-C18; Geological Survey of Canada, 16p.
Dube, B., Williamson, K. and Malo, M. Geology of the Goldcorp Inc. High Grade Zone, Red Lake Mine, Ontario: an update, Geological Survey of Canada Current Research, 2002-C26, Catalogue No.M44-2002/C26E-IN
Goldcorp Inc. Website, www.goldcorp.com
David K. Joyce Website, www.davidkjoyceminerals.com
Goldcorp publication "Outlook, 2002"
David K. Joyce is a graduate of the Haileybury School of Mines and is a mineral dealer, adjunct professor at the University of Toronto and is also a mining business development consultant. He has worked coast to coast in Canada during his career in the mining industry. He is currently president of the Walker Mineralogical Club and is past Chair of the Toronto Branch of the Canadian Institute of Mining and Metallurgy.
Stephen McGibbon is Exploration Manager at Goldcorp's Red Lake Mine. He holds a Bachelor of Science degree from Queen's University and has been active in exploration and mining for 22 years.
Many thanks to David K Joyce for permission to include his co-authored essay on "The Red Lake mine".
Photos
Mexico - Alan Leishman
South Africa - ML Baumann
Red Lake - courtesy of David K Joyce
Eagles Nest mine specimen - Stefan Ansermet
Further Reading:
Mexico
A Field Guide to the Gems and Minerals of Mexico - Paul Willard Johnson 1965
Mexico - Sept. - Oct.2003 Volume 34 Number 5, Nov. - Dec.2003 Volume 34 Number 6
Gold
Rocks and Minerals Jan.-Feb. 2004 Special Issue on Gold Vol. 79 nr 1 and 2
Lapis Gold - A noble metal.
"Some dreams come true" - Alpheus F.Williams 1948
Postscript: The Mexican part of this essay is dedicated to the memory of Walt Bowser, the best guide for mineral collectors in Mexico, and for his humanitarian work with the Mexican people.
