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, CanadaP0V 1C0
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
Mineralogical Record -
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.
