„Yogo-Saphir“ – Versionsunterschied
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==Mine history== |
==Mine history== |
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[[File:YogoSapphireExtraction.jpg|thumb|Extracting sapphires at the English Mine was similar to placer gold recovery. In this photograph, miners clean a sluice box. The fence-like contraption behind the men, or "metal riffles |
[[File:YogoSapphireExtraction.jpg|thumb|Extracting sapphires at the English Mine was similar to placer gold recovery. In this photograph, miners clean a sluice box. The fence-like contraption behind the men, or "metal riffles", has been removed from the bottom of the sluice boxes. The riffles act as a trap to capture the heavy sapphires during the "washing" process. At Yogo mines, Yogo Gulch.]] |
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During the Montana Gold Rush of 1878 about one thousand men came to Yogo Creek, Montana as a result of a gold strike and the mining camp of Yogo City flourished for about three years; before long few people were left. Gold had first been discovered there in 1866 but those prospectors were chased off by the local natives. At that time, Yogo Creek was one of the gold-bearing streams in Montana that had not been actively mined.<ref name=voynickcreek/> Yogo Creek and Yogo Gulch are located in the [[Little Belt Mountains]], [[Judith Basin County]], [[Montana]], west of [[Lewistown, Montana]], east of [[Great Falls, Montana]]. Millie Ringold, a former slave born in 1845, had settled in [[Fort Benton, Montana]] after having worked as a nurse and servant for an army general. Millie promptly left for the Yogo gold fields, selling her boarding house in Fort Benton and setting up a hotel, restaurant, and saloon. She also sang and played music. She remained there until she died in 1906 and was considered Yogo City's most prominent citizen, the last resident of the city.<ref name=voynickmillie>{{harvnb|Voynick|1985|p=21}}</ref>{{r|millie}} Only bits of gold and blue pebbles were found. It was not until late 1895 when someone finally bothered to investigate the blue pebbles. In that year Jake Hoover sent a cigar box full of them that he had collected while mining gold to Tiffany's in New York for appraisal by gemologist Dr. [[George Frederick Kunz]], the most reknowned American gemologist of the time.{{r|mtgem}}<ref name=voynickkunz>{{harvnb|Voynick|1985|pp=3-4, 29-31}}</ref> Impressed by their quality and color, Kunz pronounced them “the finest precious gemstones ever found in the United States".{{r|gemgallery}}<ref name=voynickkunz2>{{harvnb|Voynick|1985|p=31, 29-31}}</ref> Tiffany's sent Hoover a check for $3,750 along with a letter that described the blue pebbles as “sapphires of unusual quality.” Sheepherder Jim Ettien found the sapphire mother lode, the Yogo dike, in February 1896 while following a line of gopher holes, and sold it to Hoover.{{r|trigon}}{{r|bigsky}}<ref name=voynickgopher>{{harvnb|Voynick|1985|pp=32-35}}</ref> Hoover eventually sold his interest his 8 original mining stakes known as the "New Mine Sapphire Syndicate" to his two partners for $5,000.{{r|gemgallery}}{{r|usgs1908}} |
During the Montana Gold Rush of 1878 about one thousand men came to Yogo Creek, Montana as a result of a gold strike and the mining camp of Yogo City flourished for about three years; before long few people were left. Gold had first been discovered there in 1866 but those prospectors were chased off by the local natives. At that time, Yogo Creek was one of the gold-bearing streams in Montana that had not been actively mined.<ref name=voynickcreek/> Yogo Creek and Yogo Gulch are located in the [[Little Belt Mountains]], [[Judith Basin County]], [[Montana]], west of [[Lewistown, Montana]], east of [[Great Falls, Montana]]. Millie Ringold, a former slave born in 1845, had settled in [[Fort Benton, Montana]] after having worked as a nurse and servant for an army general. Millie promptly left for the Yogo gold fields, selling her boarding house in Fort Benton and setting up a hotel, restaurant, and saloon. She also sang and played music. She remained there until she died in 1906 and was considered Yogo City's most prominent citizen, the last resident of the city.<ref name=voynickmillie>{{harvnb|Voynick|1985|p=21}}</ref>{{r|millie}} Only bits of gold and blue pebbles were found. It was not until late 1895 when someone finally bothered to investigate the blue pebbles. In that year Jake Hoover sent a cigar box full of them that he had collected while mining gold to Tiffany's in New York for appraisal by gemologist Dr. [[George Frederick Kunz]], the most reknowned American gemologist of the time.{{r|mtgem}}<ref name=voynickkunz>{{harvnb|Voynick|1985|pp=3-4, 29-31}}</ref> Impressed by their quality and color, Kunz pronounced them “the finest precious gemstones ever found in the United States".{{r|gemgallery}}<ref name=voynickkunz2>{{harvnb|Voynick|1985|p=31, 29-31}}</ref> Tiffany's sent Hoover a check for $3,750 along with a letter that described the blue pebbles as “sapphires of unusual quality.” Sheepherder Jim Ettien found the sapphire mother lode, the Yogo dike, in February 1896 while following a line of gopher holes, and sold it to Hoover.{{r|trigon}}{{r|bigsky}}<ref name=voynickgopher>{{harvnb|Voynick|1985|pp=32-35}}</ref> Hoover eventually sold his interest his 8 original mining stakes known as the "New Mine Sapphire Syndicate" to his two partners for $5,000.{{r|gemgallery}}{{r|usgs1908}} |
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Version vom 3. November 2011, 23:55 Uhr
Yogo sapphires are mined in Yogo Gulch, Montana, and are a special cornflower blue color variety of corundum. Corundum is crystalline aluminum oxide, Al2O3,[1] and the second hardest mineral (rating 9) on the Mohs scale of mineral hardness. The chemical structure of Yogos is Al2O3 + NaAlSi3O8.Vorlage:R Red corundum is called ruby and all other colors of corundum are called sapphires.Vorlage:R The cornflower blue color is provided by trace amounts of iron and titanium.Vorlage:R Yogo sapphires were designated the Montana state gem, along with Montana agates, in 1969 and are rarer than diamonds.Vorlage:R In Piegan Blackfeet "yogo" means "blue sky",Vorlage:R though there is some dispute about its true meaning in Piegan Blackfeet.[2] Yogo Gulch is 15 miles southwest (SW) of Utica, Montana and 45 miles westsouthwest (WSW) of Lewistown, Montana, all located in Fergus County, Montana.Vorlage:RVorlage:R[3] Yogos are considered among the finest sapphires in the world,Vorlage:R and the finest by some gem experts.[4]
Mineralogy
Most corundum is mined from the sand and gravel created by the weathering of metamorphic rock, including sapphires found in Montana other than Yogo. The other sites include the Missouri River, Rock Creek, and Dry Cottonwood Creek.Vorlage:R However, most sapphires found at Yogo Gulch must be mined from hard rock, "in situ". This and American labor costs make mining Yogos fairly expensive.Vorlage:RVorlage:RVorlage:R The Yogo sapphire deposit is a silica-poor lamproite igneous rock dike cutting into limestone that intruded a fissure into the earth.[1] It varies from a few feet to almost 100 feet in width, averaging eight feet wide, and is over five miles long and 7000 feet deep.Vorlage:RVorlage:RVorlage:R It contains large amounts of biotite and pyroxene.Vorlage:RVorlage:R
Sapphires were first found in the United States on May 5, 1865 by Ed Collins in the Missouri River in Lewis and Clark County, Montana.[5] They have subsequently been found in several other parts of central and western and Montana and are collectively referred to as "Montana sapphires". By 1890 the British-owned Sapphire and Ruby Mining Company had bought several thousand acres of land where Montana sapphires were found but the venture failed after a few years due to fraud perpetrated by the owners.[6] Corundum was found at Dry Cottonwood Creek near Butte in 1889, Rock Creek near Philipsburg in 1892, and at Quartz Gulch near Bozeman in 1894.[7]
The term "Yogo sapphire" refers only to sapphires from the Yogo Gulch. Sapphire mining at Yogo Gulch began in 1895. Floods damaged the mines there so badly in 1923 that the mines never fully recovered. Yogo sapphires are unique among the world's sapphires: they lack color zoning, free of cavities, do not need heat treating because their cornflower blue coloring is uniform and deep, are generally free of inclusions, and they have high uniform clarity. Unlike Asian sapphires, they maintain their brilliance in artificial light.[8] Yogos also have a trigon pattern,Vorlage:R with rhombohedral crystals, a feature which is absent from sapphires from other parts of Montana.Vorlage:RVorlage:R These rhombohedrons are almost always less than 1mm in thickness and appear like striations.Vorlage:R The United States Geological Survey considers them among the world's finest sapphires. However, their rough is small and flat, so large pieces (over 2 carats) of cut Yogo gems are rare. Most cut pieces are under 1 carat. The largest recorded Yogo rough was found it 1910, was 19 carats in size, and was cut into an 8 carat gem.Vorlage:R Yogos tend to beautiful, small, and very expensive. About 2% of Yogos are in colors other than blue, almost always purple, very rarely reddish. Sapphires found in the other parts of Montana come in a variety of colors.Vorlage:RVorlage:RVorlage:RVorlage:R It is believed than Yogos are almost always blue rather than coming in a wide variety of colors as with other Montana sapphires is that their bedrock had a much longer cooling time. The largest cut Yogo is a 10.2 carat gem held by the Smithsonian Institution.Vorlage:RVorlage:R
Mine history
During the Montana Gold Rush of 1878 about one thousand men came to Yogo Creek, Montana as a result of a gold strike and the mining camp of Yogo City flourished for about three years; before long few people were left. Gold had first been discovered there in 1866 but those prospectors were chased off by the local natives. At that time, Yogo Creek was one of the gold-bearing streams in Montana that had not been actively mined.[2] Yogo Creek and Yogo Gulch are located in the Little Belt Mountains, Judith Basin County, Montana, west of Lewistown, Montana, east of Great Falls, Montana. Millie Ringold, a former slave born in 1845, had settled in Fort Benton, Montana after having worked as a nurse and servant for an army general. Millie promptly left for the Yogo gold fields, selling her boarding house in Fort Benton and setting up a hotel, restaurant, and saloon. She also sang and played music. She remained there until she died in 1906 and was considered Yogo City's most prominent citizen, the last resident of the city.[9]Vorlage:R Only bits of gold and blue pebbles were found. It was not until late 1895 when someone finally bothered to investigate the blue pebbles. In that year Jake Hoover sent a cigar box full of them that he had collected while mining gold to Tiffany's in New York for appraisal by gemologist Dr. George Frederick Kunz, the most reknowned American gemologist of the time.Vorlage:R[10] Impressed by their quality and color, Kunz pronounced them “the finest precious gemstones ever found in the United States".Vorlage:R[11] Tiffany's sent Hoover a check for $3,750 along with a letter that described the blue pebbles as “sapphires of unusual quality.” Sheepherder Jim Ettien found the sapphire mother lode, the Yogo dike, in February 1896 while following a line of gopher holes, and sold it to Hoover.Vorlage:RVorlage:R[12] Hoover eventually sold his interest his 8 original mining stakes known as the "New Mine Sapphire Syndicate" to his two partners for $5,000.Vorlage:RVorlage:R
Yogo City was briefly known as Hoover City.Vorlage:R Jake Hoover worked with and remained lifelong friends with western painter Charles Marion Russell. Russell stated he learned most of his frontier skills from Hoover.[13] The nearby town of Utica was featured in Russell's 1907 painting A Quiet Day in Utica, which was originally known as Tinning a Dog. Russell himself, Hoover, and Ringold are depicted in the painting.[14]Vorlage:RVorlage:RVorlage:R
In 1896, two other Americans staked mining claims at six other sections of the Yogo the dike in areas Hoover had deemed unfit for mining. This became known as the "American Mine", owned by the Yogo American Sapphire Company.Vorlage:R By 1899 gem merchants — Johnson, Walker and Tolhurst, Ltd. of London paid $100,000 for the New Mine Sapphire Syndicate, which became unofficially known as the "English Mine". This site was five miles from Yogo City.Vorlage:R One of the Englishmen who came was Charles Gadsden of Berkhamsted. By 1900 there was little left of the gold mine. Ringold was still working gold claims. By 1902 Gadsden was promoted to resident supervisor of the English Mine and he quickly turned the mine's focus to sapphires. Weight-for-weight rough sapphires are worth much more than gold and Gadsden's security measures resulted in the English Mine never being robbed as far as is known. Millie became known as a superb cook at the English Mine but by 1903 she had fallen on hard times and passed away. The English Mine flourished until the 1920s when it finally succumbed to floods and hard economic times in 1929. The "English Mine" had recovered more than 16 million carats of rough sapphires that were valued at $2.5 million. Subsequently a series of several other firms mined the sapphires but with marginal success.Vorlage:RVorlage:R About $25 million of gemstone had been recovered by all mines at Yogo.Vorlage:R At least 28 million carats are estimated to still be in the ground.Vorlage:RVorlage:R
Operations at the English Mine were more profitable than at the American Mine, largely because of the mining and management techniques employed. Roughs from the English Mine were shipped to London and sold in Europe, often as sapphires from the Far East. Ownership of the American Mine changed often. In 1913 the Yogo American Sapphire Company went bankrupt and was bought by New Mine Sapphire Syndicate, which quickly recouped its purchase price by washing the tailings left behind by the American Mine.Vorlage:R
The mine was eventually sold for back taxes and went through a long series of owners. Hobbyists and picknickers would often gather loose rough. Herman Yaras of California bought the mine in 1969. He sold it to Chikara Kunisaki, a California celery farmer, who formed a mining company called Roncor. This eventually led to what is now called Sapphire Village, where people can gather their own sapphires. Kunisaki has a home in Sapphire Village. Roncor also sold home sites with limited mining rights at Sapphire Village. Roncor sold the mine to Intergem of Colorado, which strip mined a large part of the eastern end of the dike. Intergem mined millions of carats but could not conclude its purchase from Roncor and Roncor regained full ownership. Then a Canadian company called Pacific Cascade Sapphires began to operate a mining lease from Roncor but ran out of funds before becoming successful and their option expired. Amex Engineering had the next lease and had some success in the middle and eastern portions of the dike but decided not to continue. Roncor retains control today but the all the mine sites except for Sapphire village are inactive.Vorlage:R
While the various companies attempted mine leasing with Roncor, two local married couples discovered a new site at Yogo Gulch in January 1984 by following a trail to an unused section of the dike that had previously deemed unsuitable. They began mining the site and named it the "Vortex Mine". The mine shaft went 280 feet down and found two Yogo ore bearing veins. The mine was successful for years but success declined and the Vortex Mine closed in 2004. A new owner bought Vortex in 2008 and is in operation as of late 2011. Its operations are environmentally friendly, using methods such as recycling all water and not using chemicals.Vorlage:R As of 2011, there is also mining activity at Sapphire Village, though the Roncor mines are inactive.Vorlage:RVorlage:RVorlage:R
While on a weight-for-weight basis sapphires are worth more than gold and the Yogo mines have produced more dollar value than several gold strikes, Yogos require hard rock mining and marketing, whereas gold is easier to identify and then merely requires digging and selling.[15]
Usage
Paulding Farnham (1859-1927) used these stones to great advantage in several pieces he designed for the 1900 Exposition Universelle in Paris,Vorlage:R where Yogos received a medal for color and clarity.Vorlage:R
Due to the rarity of large rough, prices for gems begin rising sharply when they are over a half carat, and skyrocket when they are over one carat.Vorlage:RVorlage:RVorlage:R
Notes
References
- Stephen M. Voynick: Yogo The Great American Sapphire. March 1995 printing, 1987 Auflage. Mountain Press Publishing, 1985, ISBN 0-87842-217-X.