The 29th annual FM-MSA-TGMS Tucson Mineralogical Symposium classic mineral localities of the United States.
The 29th Annual Tucson Mineralogical Symposium sponsored by the Mineralogical Society of America, Friends of Mineralogy, and the Tucson Gem and Mineral Society will be held on Saturday, February 16, 2008, at the Tucson Convention Center. Admission is free and everyone is welcome. The theme of both the Show and the Symposium is Classic Mineral Localities of the United States. The popularity of this theme has resulted in a record number of symposium talks, as the following pages of abstracts certainly attest.
It is difficult to define a "classic" mineral locality and derive a list of such localities from the definition. Only one book has come close to successfully doing so: Gem and Crystal Treasures by Peter Bancroft (1984), written almost 25 years ago. Of the 100 worldwide localities described in that book, only 24 are within the United States. Most could have been anticipated, although his list included a few surprises, such as the Yogo Gulch, Montana sapphire locality and the Virgin Valley, Nevada precious opal locality. Three other localities in this very short list were California gem pegmatite occurrences. What must be considered in such a list, particularly if it is to reflect only occurrences in one quite large and mineral-rich country--which, in the case the 2008 Tucson Gem and Mineral Show, is the United States of America? Should the "classic" occurrence be of great historical significance, such as those mentioned or described early in our mineralogical history by Archibald Bruce (1814) or Samuel Robinson (1825), even though few if any localities of this kind are important to today's collector? Should the location have produced an exceptionally wide array of rare and unusual minerals, as have the mines of Franklin and Sterling Hill, New Jersey, many species from which, although not of great attractiveness, are nevertheless of immense interest? Should the locality have produced incomparably beautiful, widely distributed specimens of an important species, such as Red Cloud mine wulfenite or Sweet Home mine rhodochrosite? Must the locality be a single mine or prospect, or can similar occurrences forming a district be considered? Or should the locality have been the source of an overwhelming volume of good specimens of a common mineral such that the occurrence is known far and wide, even to non-collectors, e.g. Hot Springs, Arkansas quartz? Perhaps any, some, or all of the above criteria, and more, must be considered. This was the conundrum facing the group of collectors, curators, and dealers who compiled the master list of classic localities featured at this year's Tucson show. Over the past 24 months exceptional specimens from each locality have been identified and borrowed for display during this single event. Most have been photographed for inclusion in the companion book (American Mineral Treasures), published specifically to document this year's show and provide background on each locality. It is, therefore, with great interest and anticipation that we are at last given the opportunity to critique the final group of classic occurrences and see for the first time the assembled great specimens from them, many of which have not been placed on public display before. A number of these localities are described in our symposium and we trust that all attendees will be both enlightened and entertained.
BANCROFT, P. (1984) Gem and Crystal Treasures. The Mineralogical Record, Tucson, 488 p.
BRUCE, A. (1814) The American Mineralogical Journal. Collins and Company, New York, 270 p.
ROBINSON, S. (1825) A Catalogue of American Minerals with their Localities. Cummings, Hilliard, and Company, Boston, 316 p.
Minerals and History of the Red Cloud Mine, Arizona
Aspects of the early history of the Red Cloud mine were revealed when Wayne Thompson began excavating the near-surface zones of the mine in 1996, turning up new evidence that the Red Cloud ores were originally milled right on the edge of the dike starting around 1881. Mining artifacts were discovered in the backfilled portion of the mine's surface workings along the north-south trench. Thompson deepened this trench by 40 to 60 feet, and in the process many old drifts were revealed that had exploited silver-rich galena veins. Printed material and a toy doll found in the deep drifts and inclines indicated that families with children lived at the mine around 1881.
The town of Silent, very close by, had a store and a saloon with an outhouse behind the store. In recent years the outhouse was dug out to see what historical treasures it might contain. A partially filled incline just south of the old Silent townsite, a short distance from the north end of the modern entrance to the Red Cloud mine, yielded an old rawhide ore bag in very good condition. A little farther south, a path led to the Red Cloud mine, and during a very rainy year a previously unknown incline with collapsing timbers was revealed. Mining artifacts were discovered, along with World War II-era papers nailed to the walls, indicating assay values.
A zone was found surrounding an area to the north, near the modern entrance to the Red Cloud mine, containing fluorescent minerals similar to some of those found at Franklin, New Jersey, including red-fluorescing calcite and green-fluorescing willemite. Emplaced in the main dike, of course, was the weathering galena which yielded the lead that produced the famous Red Cloud wulfenites. A rare occurrence of copper minerals was found in the northwest corner of the mine, containing diaboleite pseudomorphs and other copper-containing species.
The area in the vicinity of the Red Cloud mine is very interesting as well, including many mines such as the Black Rock, the Princess and the Hamburg. They were worked in the early 1880's and their silver-lead ore was hauled down to the Colorado River to be milled, then shipped out on paddlewheel boats.
Fallbrook Gem and Mineral Museum
260 Rocky Crest Rd
Fallbrook, CA 92028
The Gem and Rare-Element Pegmatites of Southern California
Gem tourmaline was first discovered in Southern California in 1872, on Thomas Mountain in Riverside County. It wasn't until 1898, however, that a local "gem rush" began with the discovery of the tourmaline-rich deposits in Mesa Grande. Gem-producing pegmatites were soon discovered in Pala, Ramona and other districts throughout the area. Much of the gem mining was supported by a demand for pink carving-grade tourmaline which was fashionable in China. As a result, most tourmaline was originally mined for lapidary uses and relatively few crystal specimens survive from this period. With the overthrow of the Chinese dynasty in 1912, this market dried up, causing the local gem market to crash.
After 1912, pegmatite mining activities were limited in Southern California, but attempts to reopen a number of the more famous mines began in the late 1950's. As a result, spectacular finds have been made at a number of mines, including the Himalaya, Stewart, Tourmaline Queen, White Queen and Little Three, during the latter half of the 20th century.
The Southern California pegmatite province is made up of numerous individual districts, ranging from central Riverside County southward through San Diego County and into the northern portion of the Baja peninsula. The pegmatites are, for the most part, hosted by the Cretaceous-age Peninsular Ranges Batholith, and are believed to be related to its formation around 100 million years ago. Compositionally, most of the southern California pegmatites belong to the LCT (Lithium-enriched, Cesium-enriched, Tantalum > Niobium) category according to the classification proposed by Cerny (1991). Although there are perhaps tens of thousands of granitic pegmatites scattered through the region, few have ever yielded significant gems or specimens, and fewer still have yielded enough to sustain commercial development. The few that have, however, have given up some of the most famous and well-known gem mineral specimens in the world.
The pegmatite districts in Riverside County are scattered and poorly defined compared to those farther south. A few of the pegmatites around Cahuilla Mountain have been the most productive in the area. The Fano mine is known for its occasional production of gem aquamarine crystals and schorl. The Lithia Dike has been the source of small amounts of high-quality pink and bicolored tourmaline in recent years.
Two minor pegmatite districts, Chihuahua Valley and Aguanga Mountain, occur just over the San Diego County line. The best known prospect in the Chihuahua Valley district is the Blue Lady mine, which has yielded numerous dark, indigo-blue tourmaline crystals, along with the occasional aquamarine and morganite specimen. Large, well-formed crystals of microcline have been recovered as well. Two mines on Aguanga Mountain--the Maple Lode and the Ware mine (also known as the Mountain Lily or the Emeralite mine) have periodically produced small amounts of colorless to blue topaz, and small crystals of bright blue and blue-pink bicolored tourmaline.
The best known and most productive districts occur in north-central San Diego County. The Pala district, near a village of the same name, consists of numerous pegmatites centered on three hills. The westernmost, Queen Mountain, is host to a number of well-known mines including the Stewart, Tourmaline Queen and Tourmaline King, which have been the source of numerous spectacular specimens of pink and bicolored tourmaline. Chief Mountain, in the center of the district, is home to the Pala Chief mine (known for producing high-quality specimens of both colored tourmaline and kunzite) as well as the Elizabeth R, source of some very good morganite in recent years. To the east, Hiriart Mountain hosts numerous pegmatites, including the Katerina, Vandenberg and White Queen, which have yielded fine specimens of kunzite and morganite. Kunzite, the lilac-colored gem variety of spodumene, was first identified from the pegmatites of Hiriart Mountain.
About 25 miles east of Pala, near Henshaw Reservoir, is the Mesa Grande district. Though numerous pegmatites in the district have produced small amounts of gem and specimen materials, its fame rests largely on the Himalaya mine, which during the course of the past century has been one of the most productive gem pegmatites in North America, if not the world. Aside from yielding literally tons of colored tourmaline, the Himalaya mine has been the source of numerous specimens of other minerals, including fluorapatite, hambergite, stibiotantalite, stilbite, quartz, lepidolite and feldspars. Other mines in the district include the San Diego, Esmeralda, Cota, Payne and Green Ledge.
The Rincon district is located between Pala and Mesa Grande, and has been the source of minor amounts of colored tourmaline and gem aquamarine in the past. The best known mines in the district are the Clark, Mack and Victor. Most of the district is on private or tribal lands, and very little material has been mined from these pegmatites in recent years.
The Ramona district is located in central San Diego County near the town of the same name. The most famous and productive pegmatite in the district has been the Little Three mine. The mine actually exploits two adjacent pegmatites of markedly different character. The Main Little Three dike has been the occasional source of some spectacular specimens of blue topaz, which rival those found in the Alabashka area of the Ural Mountains, Russia in form and color. The dike has also produced numerous well-formed crystals of dark green tourmaline, commonly associated with smoky quartz and feldspars. The nearby Hercules-Spessartine dike has been the source of some of the finest near-end-member spessartine garnet found anywhere. The material is typically rather corroded and is more suitable for lapidary use, but some spectacular specimens have occasionally been found.
The Jacumba district is a remote and poorly prospected region near the Mexican border. A major find of gem spodumene was made there in 1975 at a prospect known as the Beebe Hole. This claim has since been merged with the neighboring Pack Rat mine and, while no more finds of spodumene have been made, the mine did produce some gem aquamarine, spessartine, fluorapatite and rare phosphate minerals during the 1990's.
Although most pegmatite mines in southern California have once again fallen into inactivity, occasional finds continue to be made. Most important has been the remarkable finds of pink tourmaline and beryl at the previously unimportant Cryo-Genie mine in 2001-2003. The Stewart, Elizabeth R and Pala Chief mines also continue to be worked, producing the occasional find.
CERNY, P. (1991) Rare-element pegmatites (parts 1 and 2). Geoscience Canada, 18 (2), 49-81.
FISHER, J. (2002) Gem and rare-element pegmatites of Southern California. Mineralogical Record, 33 (5), 363-407.
FOORD, E. E., SPAULDING, L. B., MASON, R. A., and MARTIN, R. F. (1989) Mineralogy and paragenesis of the Little Three mine pegmatites, Ramona district, San Diego County, California. Mineralogical Record, 20 (2), 101-127.
JAHNS, R. H., and WRIGHT, L.A. (1951) Gem and lithium bearing pegmatites of the Pala District, San Diego County, California. California Division of Mines Special Report 7A, 72 p.
KUNZ, G. F. (1905) Gems, jeweler's materials, and ornamental stones of California. California State Mining Bureau Bulletin 37, 171 p.
KAMPF, A. R., GOCHENOUR, K., and CLANIN, J. (2003) Tourmaline discovery at the Cryo-Genie mine, San Diego County, California. Rocks & Minerals, 78 (3), 156-168.
RYNERSON, F. J. (1967) Exploring and Mining for Gems and Gold in the West. Naturegraph, Healdsburg, California, 204 p.
P. O. Box 77774
San Francisco, CA 94107
Arkansas Quartz Crystals--The Leitmotif of Quartz Morphology for Collectors
The Hot Springs, Arkansas area is world famous for its sharp, clear, lustrous, exquisitely well-formed quartz crystals. They are abundant over a considerable area and were well-known and even exploited by the Indians before Spanish explorers penetrated the area. President Jefferson was curious about the area and sent an expedition to investigate it.
The hot springs elicited interest and attracted tourists early in the 19th century. As transportation improved, more tourists were attracted. Locals quickly realized that tourists, then as now, constituted a great market for the quartz crystals, which were dug up by the wagonload to supply this demand and were eventually distributed all around the U.S. and Europe. Clear crystals were even cut and polished and offered under the unfortunate misnomer of "Arkansas Diamonds."
The crystal morphology of Arkansas quartz crystals is relatively simple. It is easy to acquire good examples of most of the crystal forms and growth habits of quartz on a visit to the area. A dedicated collector can spend many happy hours or days picking through the abundant offerings of the locals or digging at the many fee-digging areas.
The quartz crystals occur in steeply dipping cracks or fissures in sedimentary rocks, especially sandstone formations. The veins are surprisingly close to monomineralic from a collector's point of view, especially in the sandstones. Often there has been movement in the veins during crystal formation, causing crystals to break and be regrown. This often produces unusual, highly collectible habits, sometimes bordering on the bizarre. There will be some discussion of the factors which determine the various crystal habits shown by Hot Spring quartz crystals, especially those which are most interesting and desirable. What is most treasured by collectors and museums, however, is the large, clear, sharply formed classic "rock crystal" quartz.
6331 Fairmount #306
El Cerrito, CA 94530
Bisbee, Arizona The "Classic" American Mineral Locality
The wonderfully rich copper deposits at what is now Bisbee, Arizona were discovered and exploited at a most opportune time for mineral appreciation and preservation. Late in the 19th century there was a period of great public curiosity concerning all things natural, and minerals were no exception, particularly the strikingly beautiful copper carbonates (azurite and malachite) that began to appear from the remote deserts of southeastern Arizona. Museums and private collectors alike were anxious to acquire samples of what were, at the time, the finest known examples of these colorful species.
Fortunately, the mines at Bisbee were owned and operated by men of vision who possessed a true sense of responsibility for the recovery and preservation of these natural wonders; thus many thousands of fine minerals were saved for our continued enjoyment today. This is an overview of that combination of fortuitous events which gave Bisbee the legacy of its great minerals and true claim to the title of "America's classic mineral locality."
GRAEME, R. A. (1981) Famous mineral localities: Bisbee, Arizona. Mineralogical Record, 12 (5), 258-319.
GRAEME, R. A. (1993) Bisbee revisited: an update on the mineralogy of this famous locality. Mineralogical Record, 24 (6), 421-436.
Richard W. Graeme
158 Miroquesdada #2100
San, Isidro, Lima 27
Crater of Diamonds State Park, Arkansas--An Overlooked Treasure
The year 2006 was the celebration of the 100th anniversary of the discovery of diamonds in the Prairie Creek diatreme near Murfreesboro, Arkansas by John Huddleston, a local pig farmer. Thanks to poor financing and, by modern standards, even poorer security measures, the pipe never proved commercially viable. Some even claimed that the DeBeers syndicate was behind the failures, but much of that early history is now lost in time and memory--overshadowed by the thousands of tourists and many local diggers who visit the pipe every year. It is known that tens of thousands of diamonds were recovered by both commercial and non-commercial efforts in the many years before the area became state property in 1972. And since then 25,000 more crystals have been documented. Modern facilities now greet the visitor, whether they are seasoned collectors or first-time hopefuls.
I will discuss some of the early history of discovery and the people involved in it, and will present some information about the early mining efforts. Also the park's improvements since 1972 will be discussed, as will new statistical information of interest, including a prediction of how long the park will continue to be a source of diamonds for collectors and visitors. Of particular interest will be some images of several of the larger diamonds discovered during 2006. Each day that passes, the soil gives up another couple of diamonds to eager hunters. Experience often gives way to beginner's luck when finders-keepers is played at this most unusual park!
J. Michael Howard
16000 Vimey Woods Road
Mabelvale, AR 72103
The Mount Antero Mineral Locality, Chaffee County, Colorado: A Collecting History
The blue beryl ("aquamarine") crystals from Mount Antero in Colorado were first introduced to the mineralogical community by "Nels" Nelson Daniel Wanemaker via a letter from Roselle T. Cross to George F. Kunz in 1885. The discovery of aquamarine was soon followed by the recognition of phenakite, bertrandite, fluorite and topaz from the Mount Antero and Mount White areas. During the early years, from 1885 to 1893, Wanemaker sold specimens to all of the leading mineralogists and collectors in the U.S. These minerals were collected from miarolitic pegmatites, hydrothermal veins and greisens associated with the upper portions and first-crystallized parts of the peraluminous Mount Antero Granite, especially within the leucocratic variant of the granite.
After Wanemaker had moved on to other ventures, several other miners tried their hand on Mount Antero, of whom only John D. Endicott from Canon City documented his success. From 1928 to 1949, Ed Over, in association with Arthur Montgomery, collected numerous specimens which were sold to leading museums and private collectors. With the rise in price of beryllium and its subsidy by the U.S. Federal government in 1952, John King of Salida, Colorado and Grady Cardwell of Texas both saw opportunity on Mount Antero for mining beryl and producing aquamarine gemstones as a by-product. This led to the first dirt road up Mount Antero and Mount White in 1956, and the reopening of the California molybdenite mine adit in 1960.
By 1962, all the business entities on Mount Antero had gone bankrupt and the claims had lapsed. Mining the Mount Antero granites for disseminated beryl had been an economic failure. In May 1969, Grady Cardwell formed a new company, North American Beryllium Corporation (NABC), reclaiming the entire south knob of Mount Antero. This company focused on trying to mine beryllium ore rather than gemstones. They were not concerned with fine crystals, and did not seriously interfere with collectors digging by hand for mineral specimens.
With the road open to amateur diggers, numerous discoveries of gem pockets were made across Mount Antero and Mount White by many collectors from the 1970's through the 1990's. Collectors such as Chuck Barnes, Eldon Bright, Bill Chirnside, Bob and Doris Drisgill, Jim Grika, Pete McCrery, John Melby, "Rosy" Horace O'Donnell, Curtis Abbott, Cliff Nicholson, Andrew Taylor, George Fisher and George Robertson made notable discoveries.
The situation changed radically in 2001 when the Cardwell family decided to focus on mining aquamarine gemstones. Accordingly, under the active supervision of fourth-generation miner Craig Cardwell, mineral collecting on the south knob of Mount Antero was restricted. These claims are still legally valid. This has forced a new generation of collectors to move their collecting activities to areas that have not been prospected since 1956, when the first road up the mountain was opened. Steve Brancato after 2001 recovered the finest matrix aquamarine specimens ever known, as well as topaz and smoky quartz. Jeff Self and associates recovered large quantities of smoky quartz and associated minerals. Bryan Lees' sublease on the Cardwell claims resulted in the 2005 discovery of the finest helvite crystals known from the locality. The 2000-2007 prospecting activity has been more intensive and surprisingly more successful than ever before, proving that the locality is far from exhausted. This activity has not been without cost and strife involving the claim holders, casual collectors, environmental activists and U.S. government employees.
Mark I. Jacobson
108 Farmington Drive
Lafayette, LA 70503
The Benitoite Gem Mine: Past, Present and Future
The Benitoite Gem mine, one of America's classic mineral localities, was discovered in 1907. Since that discovery, its history has consisted of a series of owners and lessees trying to find what the previous owners and lessees missed. Abandoned and sold at different times, the mine seems to keep shouting back, "I'm not quite dead yet!"
We have the early miners to thank for the continued life of this locality. Dynamite and punch presses were used to separate benitoite from the host rock. Although it was soon learned that hydrochloric acid could remove the natrolite that almost always covered the crystals and matrix, the acid treatment was found to take too long, so the miners continued to employ the crude but fast techniques, ruining countless thousands of specimens and gemstones while spreading small crystal fragments all over the area.
After the mine was closed in 1913 by Roderick Dallas, it was briefly reopened in 1933, then closed again, then leased in the 1940's to a Mr. Hotchkiss. From 1952 to 1967, Mr. Cole leased the mine and put ads in Rock and Gem magazine inviting the public to come and collect all they wanted for under $1 per pound! In 1967, the mine was leased to William Forrest and Elvis "Buzz" Gray, who worked the dumps until 2000. In 1987 they purchased the mine from the Dallas family. In 2000 the mine was sold to Bryan Lees' company, Benitoite Mining, Inc., in Golden, Colorado. In June of 2005, it was announced that the mine was closed, supposedly marking the end of yet another great American locality.
But that is not the end of the story. In the summer of 2005, the mine was sold to David Schreiner of Coalinga, who has recently reopened the mine to the public on a fee-digging basis. In February of 2006, Dave's brother Terry found a piece of rough that cut the world's third largest clean faceted benitoite (8 carats). Not bad for a "dead" locality!
What does the future hold for the Benitoite Gem mine? If the past is any guide, more people will write it off as dead just before something else amazing is discovered there.
65 Washington Street #264
Santa Clara, CA 95050
Iridescent and Other Fluorites from the Findlay Arch, Ohio
Ohio has produced some of the most beautiful and unique fluorite specimens in North America. These have all come from the Findlay Arch mineral district, located in northwestern Ohio and extending into Allen and Adams counties in Indiana and Monroe County in Michigan. The Findlay Arch is a large north-south-trending, subsurface geological structure (basin divide) made up of sedimentary rocks ranging in age from mid-Silurian to mid-Devonian. Nearly 100 minor mineral occurrences define this district, and the minerals of the district are chiefly found in the open spaces provided by fossil molds, gypsum molds, vugs, caves, and fractures within dolostones. Prominent locations include Bellevue/Flat Rock, Bluffton, Junction, Delphos, Clay Center, Genoa, Custar, Woodville, Gibsonburg, Maumee, Lime City and Lima in Ohio, Newport in Michigan and Fort Wayne in Indiana. Fluorite crystals range in size from sub-millimeter to 10 or more centimeters. One of the most notable features of some specimens is surface iridescence--usually gold or brown, but also showing blue, green, violet and orange-red colors. This effect was recently shown to be due to a thin film of hydrocarbons on the fluorite surfaces. A noteworthy characteristic of these specimens is that the iridescent film inhibits the fluorescence of the fluorite beneath.
Attractive non-iridescent fluorite is also found among the Findlay Arch deposits. Most commonly the crystals are lustrous yellow to dark brown, and fluoresce strongly under longwave ultraviolet light. Other collectible specimens include color-zoned crystals, such as those from the Auglaize and Delphos quarries that have deep purple cores overgrown by a later generation of colorless fluorite. Such a specimen has won the awards for best miniature at the Tucson and Denver shows. A particularly aesthetic combination common at the Auglaize quarry is the sparse overgrowth of lustrous, transparent, deep purple or pale violet fluorite crystals on a druse of iridescent brown fluorite.
Crystal morphologies are typically simple and are dominated by the cube. However, dodecahedral, hexoctahedral, tetrahexahedral and other modifications of the cube have been found, and at Delphos and Lima unusual botryoidal-appearing clusters of cubic crystals and needles have been found in the same geologic layer.
5280 Stover Road
Ostrander, Ohio 43061
Department of Geology
Oxford, Ohio 45056
What is the "Most Important" Mineral Locality in the U.S.?
Many different criteria could be used to assess the "best" or most important mineral locality in the U.S. or the world. These might include the number of mineral species found, the quality and abundance of its specimens, and the area's contributions to the scientific literature. Some of the most noteworthy U.S. localities would certainly include the pegmatite districts of the Pikes Peak batholith in Colorado, San Diego County in California, and various localities in Maine, North Carolina, and Virginia. Non-pegmatite deposits would include Bisbee, Arizona; Butte, Montana; and the mid-continent lead-zinc-fluorite districts. Some localities might merit consideration for their spectacular abundance of one mineral, such as the wulfenite from the Red Cloud mine in Arizona.
A good case could be made for Franklin and Sterling Hill, New Jersey, as the nation's premier mineral localities. Reasons would include their large (340+) number of species, number of type species and number of unique species, as well as their wide familiarity to collectors and their abundant representation in museums and in the scientific literature--not to mention the area's unique abundance of spectacular fluorescent minerals.
How does the rest of the world compare? Some contenders for value, quality and abundance of specimens could be the pegmatite districts of Minas Gerais, Brazil, and of Madagascar, Pakistan, and China; Tsumeb, Namibia; Broken Hill, New South Wales; and the Poona, India zeolite region. Localities prominent for their number of mineral species would include Mont Saint-Hilaire, Quebec; Langban, Sweden; and the alkaline igneous complexes of Ilimaussaq, Greenland, and Khibiny and Lovozero in the Kola Peninsula, Russia.
Peter J. Modreski
U.S. Geological Survey, Mail Stop 150
Box 25046 Federal Center
Denver, CO 80225
The Elmwood Zinc Mine, Carthage Tennessee
The Elmwood Zinc mine is located in central Tennessee near the town of Carthage in Smith County. The orebodies--classic examples of Mississippi Valley-type hydrothermal deposits--are found within brecciated areas, caves and solution cavities of Ordovician-age carbonates, both limestone and dolomite. Miners have reported drilling into some of these caves that were so large that they had to wait hours (and even, in several cases, days) for the water to drain out of the ore pockets.
Great specimens will be the focus of this talk; I will show specimens from the Elmwood mine and recount some very interesting stories associated with these pieces. The calcites and fluorites are of world-class quality and size, and are universally recognized as some of the best crystal specimens that these species can produce.
Last December, Strategic Resources Acquisition (SRA) Corporation purchased the Elmwood properties, including drills, loaders, sealers and other equipment, for $16.3 million. This group plans to have the mines in full production by early 2008, bypassing feasibility studies and moving forward with the de-watering of the mine complex. Several new shafts are contemplated in this venture. There are currently three shafts: one at Elmwood, one at Gordonsville, and one at Cumberland. There are plans for possible additional shafts in the Stonewall area. SRA has hired Dynatec to restore production at these mines. They plan to sell zinc, germanium, gallium and limestone rock for agricultural use, and they feel that the profits from these sales will help offset their operating costs. Arrangements for the commercial collecting and sale of mineral specimens are still in negotiation, with several groups actively pursuing this contract. All we can hope for is to see a rejuvenated flow of great specimens from these mines in the future.
1616 West Main Street
Lebanon, Tennessee 37087
The Mammoth-St. Anthony Mine, Tiger, Arizona
The Mammoth-St. Anthony mine at Tiger, Arizona has recorded 90 mineral species, ranging from the common to the very rare. Fine examples of cerussite, dioptase, malachite, azurite, wulfenite, smithsonite and vanadinite have been collected there, as well as some of the finest known examples of a number of rarer species such as boleite, diaboleite, caledonite, hydrocerussite, linarite, matlockite and leadhillite.
"Mammoth-St. Anthony mine" is the correct name to use when labeling specimens, especially those collected between 1939 and 1953. The mine lies about 80 kilometers north-northeast of Tucson.
From 1879 to 1914, mining efforts focused solely on gold recovery. The mines were worked for wulfenite as a source of molybdenum during World War I, but shut down shortly after the war ended. After a few false starts, mining resumed in 1935 and then shut down for good in 1953.
Scientists became interested in Tiger following the 1938 publication of Nels Peterson's Geology and Ore Deposits of the Mammoth Mining Area, Pinal County, Arizona. Richard (Dick) Bideaux performed the first comprehensive study of these deposits while doing graduate work at Harvard University.
Two miners, George Griffith and his brother Archie, collected and sold specimens for the mining company, and even the mine manager J. J. Strutzel maintained a personal collection. Starting in 1968, Magma Copper Company (the owner of the Mammoth-St. Anthony mine) allowed organized mineral club collecting on the dumps and in an open pit at Tiger, but this came to an end in 2005.
Today, small but superb suites of Tiger minerals can be seen in three Arizona museums: the University of Arizona, the Arizona-Sonora Desert Museum, and the Arizona Mining and Mineral Museum. Private collections containing excellent examples include those of Rock Currier, Evan Jones, Les and Paula Presmyk and Tony Potucek.
P.O. Box 1273
Gilbert, Arizona 85299
Amethyst Scepters from Ashaway Village, Hopkinton, Rhode Island
The eastern United States is well known for its many occurrences of amethyst. In the spring of 1981, amethyst scepter overgrowths on milky quartz crystals were discovered in Ashaway Village, Hopkinton, Rhode Island (Metropolis et al., 1986). This deposit has produced some of the most beautiful amethyst specimens found in the United States. Fine examples are on display in museums worldwide. The amethystine color ranges from faint violet to a deep purple, and the contrast of gemmy amethyst caps on opaque, porcelain-white stems is particularly aesthetic.
The amethyst specimens occur in collapsed and segmented quartz veins embedded in a thick clay unit. No surface exposure of these quartz veins has been found, and they have only been accessible where small temporary pits have been dug. Since 1985 the authors have dug at the site each year for one day only. Although the majority of good specimens were found between 1981 and 1985, important specimens have turned up during subsequent digs. Examples include fine single scepters and matrix scepters of deep purple amethyst caps on white stems; large single milky quartz crystals (up to 35 cm) with violet amethyst overgrowths that cover the termination and often extend over a significant length of one or two prism faces; and scepters with hoppered amethyst overgrowths. One exceptional specimen is a doubly terminated scepter measuring roughly 17 cm long and 7 cm wide. Most specimens found at the site, however, are milky quartz crystals with no associated amethyst. Rarely, colorless, transparent quartz crystals have been encountered.
Fluid inclusion data have been determined for the quartz crystallization, including temperatures of homogenization (94.5[degrees] to 149.7[degrees] C; mean = 124.6[degrees] C for amethyst overgrowths, and 125.5[degrees] to 186.9[degrees] C; mean = 156.4[degrees] C in the milky stems), salinity (0.2 to 15.7 eq. weight % NaCl; mean value 7.8), and oxygen and hydrogen isotopic compositions ([[delta].sup.18]O = -3.5 to -2.2 [+ or -] 0.2 [per thousand] for the milky quartz and from -6.0 to -3.1 [+ or -] 0.2 [per thousand] for the amethyst overgrowths). These data indicate that, contrary to initial speculations of an igneous origin, the quartz precipitated from low-temperature, hydrothermal meteoric waters, along with the surrounding clays, during several stages of precipitation (Rakovan et al., 1995).
METROPOLIS, W. C., RAKOVAN, J., and AVELLA, S. (1986) Amethyst sceptered quartz from Ashaway Village, Hopkinton, Rhode Island. Rocks & Minerals, 61, 247-250.
RAKOVAN, J., MITCHELTREE, D. B., BENTON, L., and AVELLA, S. (1995) Amethyst on milky quartz from Hopkinton, Rhode Island. Mineralogical Record, 26, 83-89.
Department of Geology
Oxford, OH 45056
Apple Valley Minerals
7 Homestead Avenue
Smithfield, RI 02917
Emerald Crystal Pockets of the Hiddenite District, Alexander County, North Carolina
Since the late 1870's the Hiddenite district has produced North America's largest emeralds. The current record is a 1,869-carat crystal found in 2003 on the North American Emerald Mines (NAEM) property, located on the northeast side of the 1.5 x 5-km district. Approximately 70% of the district's estimated 50,000 carats of emerald production have come from this property, including 15 of the continent's 20 largest emeralds.
Emeralds are hosted by late-metamorphic Alpine-type lensoidal quartz veins cutting Cambrian-age metasedimentary rocks of the plate-tectonic Piedmont terrane. This 160 x 1,120-km crustal block has a long deformational history involving multiple continental collisions throughout the Paleozoic. Quartz veins cut most metamorphic textures and appear to have originated as fillings of tensional fractures in the Early Mesozoic. The host rocks, originally a sequence of siliceous deltaic sediments, underwent three periods of major folding, reached mid-amphibolite grade metamorphism and are mapped as layered biotite gneiss.
Half of the veins have crystal pockets and half of the pockets contain emeralds. Crystal pockets are typically three-fourths filled with crystal breccia. Pocket minerals include quartz, muscovite, carbonates, albite, rutile, clay, beryl, sulfides and rare hiddenite and graphite. Emerald values vary widely, with collector specimens up to $500/ct and cut gemstones up to $60,000/ct. Remarkably, emerald crystals average over 50 carats each and crystals over 1,000 carats account for 8% of the total production. Pockets containing over 3,000 carats have been documented.
The typical emerald vein contains 80 [cm.sup.3] of white cryptocrystalline quartz overlying a 20 [cm.sup.3] open crystal pocket. The largest documented vein contained 17 [m.sup.3] of quartz overlying a 7 [m.sup.3] pocket filled with 7 tonnes of crystal breccia. Narrow wall-rock alteration halos are common peripheral to veins and crystal pockets.
34 Clear Creek Rd
Marion, NC 28752
Mineralogy of the Gem-Bearing Alpine-Type Quartz Veins from Hiddenite, North Carolina
Emeralds in North Carolina were first discovered from the Hiddenite area as early as 1913, when local farmers began finding crystals in plowed fields. Shortly thereafter, a new chromium-green gem variety of spodumene, later named hiddenite, was uncovered, and the region became of great scientific and gemological interest. Today, the Hiddenite area constitutes the most significant emerald-producing district in North America and is the world's only confirmed locality for hiddenite.
Emerald and hiddenite both occur in cavities within steeply dipping Alpine-type fissure quartz veins that cut across highly deformed migmatitic schists and quartz-biotite gneiss of the Inner Piedmont Belt. Accompanying the gem minerals is a suite of minerals which, together with the emerald and hiddenite, indicate low temperature-low pressure crystallization conditions. Typical minerals of the quartz veins and their cavities include albite, fluorapatite, calcite, chabazite, clinochlore, dolomite, goethite, graphite, kaolinite, muscovite, molybdenite, pyrite, pyrrhotite, quartz, rutile, siderite and tourmaline.
The mineralogy of the cavities is dominated largely by quartz, muscovite and calcite. Multiple generations of quartz (fine-grained, doubly terminated crystals, to large, transparent or milky crystals, to late amethystine scepters) and calcite (rhombohedrons, scalenohedrons, platy and hexagonal prisms) are common in most cavities. Colorless, white and gray calcite is the most abundant carbonate mineral present, whereas dolomite and siderite are less common and are generally absent in cavities that do not host emerald mineralization. White, gray and pale yellow rhombohedrons of dolomite are typically the first of the three carbonates to form, being found not only in the massive quartz portion of the vein, but also within the cavity itself. Honey-colored rhombohedrons of siderite are restricted to the emerald-bearing cavities. Dark brown pseudomorphs of goethite after siderite are common in emerald-bearing assemblages that have been subjected to weathering. Muscovite occurs as tan-colored crystals, sometimes with greenish rims. Rutile tends to form stubby, thin, elongated black to red crystals with quartz, albite or calcite. Reticulated twins of rutile frequently occur with the emerald-bearing assemblage.
Sulfides generally crystallize during the last stage of mineralization in the cavities, along with graphite and zeolite minerals, and occur in two separate vein assemblages: (1) beryl-bearing fissure veins that carry accessory pyrite, pyrrhotite, sphalerite, chalcopyrite and trace amounts of galena, and (2) spodumene-bearing veins that host pyrite, pyrrhotite, molybdenite and trace amounts of gersdorffite. Pyrite is the dominant sulfide mineral present, forming 1-mm cubes and octahedrons. Hexagonal crystals of graphite 1 mm in diameter occur included in and on the surfaces of calcite, pyrite, muscovite and chabazite. Schorl, monazite and zircon have been rarely observed in some hiddenite-bearing cavities. Chabazite-Ca is found as a late-precipitating phase in spodumene-bearing veins, but is apparently absent in emerald-bearing veins. Chabazite-Ca occurs as simple, water-clear penetration twins of pseudocubic rhombohedra and as yellow, complexly twinned, lens-shaped crystals. Clays are represented by white kaolinite and a pale green clinochlore-like mineral.
Michael A. Wise
Department of Mineral Sciences
Washington, D.C. 20560
Tellus: Northwest Georgia Science Museum
P.O. Box 3663
Cartersville, Georgia 30120
Robert B. Cook
Department of Geology and Geography
210 Petrie Hall
Auburn, Alabama 36849
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|Title Annotation:||Friends of Mineralogy, Mineralogical Society of America, and the Tucson Gem and Mineral Society|
|Author:||Gray, Julian; Cook, Robert B.|
|Publication:||The Mineralogical Record|
|Date:||Jan 1, 2008|
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