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[[File:43pearYogoSapphire.jpg|thumb|A 0.43 carat pear-shaped cornflower blue Yogo sapphire.]]
[[File:43pearYogoSapphire.jpg||right|200px|A 0.43 carat pear-shaped cornflower blue Yogo sapphire.]]


'''Yogo sapphires''' are only mined in Yogo Gulch, [[Montana]], and are a special [[cornflower blue]] color variety of [[corundum]]. Yogo sapphires are considered among the finest sapphires in the world,{{r|usgs}} and by some gem experts, the finest.<ref name=voynickfine>{{harvnb|Voynick|1985|p=vii}}</ref><ref name=voynickdep>{{harvnb|Voynick|1985|p=193}}</ref> Red corundum is called [[ruby]] and all other colors of corundum are called [[sapphire]]s.{{r|utex}} Corundum is crystalline [[aluminum oxide]],<ref name=voynickmineral>{{harvnb|Voynick|1985|pp=ix-xi}}</ref> and the second hardest mineral (rating 9) on the [[Mohs scale of mineral hardness]].{{r|trigon}} The cornflower blue color of the Yogo is provided by trace amounts of [[iron]] and [[titanium]].{{r|bluesky}} "Yogo" is said to mean "blue sky" in [[Piegan Blackfeet]],{{r|bluesky}} although there is some dispute about its true meaning in that language.<ref name=voynickcreek>{{harvnb|Voynick|1985|p=10}}</ref> Yogo sapphires are rarer than diamonds, and in 1969, were designated the Montana [[state gemstone]], along with Montana [[agate]]s.{{r|distinctly}}{{r|mtkids}}<!--actually, Montana Code Annotated section 1-1-501 says just "sapphire", see http://data.opi.mt.gov/bills/mca/1/1/1-1-505.htm (grrr) -->
'''Yogo sapphires''' are only mined in Yogo Gulch, [[Montana]], and are a special [[cornflower blue]] color variety of [[corundum]]. Yogo sapphires are considered among the finest sapphires in the world,{{r|usgs}} and by some gem experts, the finest.<ref name=voynickfine>{{harvnb|Voynick|1985|p=vii}}</ref><ref name=voynickdep>{{harvnb|Voynick|1985|p=193}}</ref> Red corundum is called [[ruby]] and all other colors of corundum are called [[sapphire]]s.{{r|utex}} Corundum is crystalline [[aluminum oxide]],<ref name=voynickmineral>{{harvnb|Voynick|1985|pp=ix-xi}}</ref> and the second hardest mineral (rating 9) on the [[Mohs scale of mineral hardness]].{{r|trigon}} The cornflower blue color of the Yogo is provided by trace amounts of [[iron]] and [[titanium]].{{r|bluesky}} "Yogo" is said to mean "blue sky" in [[Piegan Blackfeet]],{{r|bluesky}} although there is some dispute about its true meaning in that language.<ref name=voynickcreek>{{harvnb|Voynick|1985|p=10}}</ref> Yogo sapphires are rarer than diamonds, and in 1969, were designated the Montana [[state gemstone]], along with Montana [[agate]]s.{{r|distinctly}}{{r|mtkids}}<!--actually, Montana Code Annotated section 1-1-501 says just "sapphire", see http://data.opi.mt.gov/bills/mca/1/1/1-1-505.htm (grrr) -->

Revision as of 11:01, 7 November 2011

A 0.43 carat pear-shaped cornflower blue Yogo sapphire.
A 0.43 carat pear-shaped cornflower blue Yogo sapphire.

Yogo sapphires are only mined in Yogo Gulch, Montana, and are a special cornflower blue color variety of corundum. Yogo sapphires are considered among the finest sapphires in the world,[1] and by some gem experts, the finest.[2][3] Red corundum is called ruby and all other colors of corundum are called sapphires.[4] Corundum is crystalline aluminum oxide,[5] and the second hardest mineral (rating 9) on the Mohs scale of mineral hardness.[6] The cornflower blue color of the Yogo is provided by trace amounts of iron and titanium.[7] "Yogo" is said to mean "blue sky" in Piegan Blackfeet,[7] although there is some dispute about its true meaning in that language.[8] Yogo sapphires are rarer than diamonds, and in 1969, were designated the Montana state gemstone, along with Montana agates.[9][10]

Location

Sapphire mining at Yogo Gulch began in 1895.[11] Yogo Gulch is located in what was then southwestern Fergus County, Montana, 12 miles (19 km) southwest (SW) of Utica, Montana and 45 miles (72 km) west-southwest (WSW) of Lewistown, Montana. It lies east of Great Falls, Montana.[12][13][14] Yogo Gulch and Utica are now located in Judith Basin County, Montana, which was formed from western Fergus County and eastern Cascade County, Montana on December 10, 1920.[15][16] Yogo Peak (el. 8,625 feet (2,629 m)), Yogo Creek, Yogo Gulch, and the Yogo dike are located in the portion of the Little Belt Mountains that lies within Judith Basin County. The Judith River flows northeast (NE) out of these mountains towards Utica. Pig-Eye Basin lies to the east of the river and the Yogo area to the west. Yogo Peak is about 15 miles (24 km) to the west of the Judith River. Yogo Creek flows from there southeast (SE) to its confluence with the Middle Fork of the Judith River, just a few miles west of where the Middle Fork meets the Judith River. Yogo Gulch is the portion of Yogo Creek just before it meets the Middle Fork. Yogo dike is just a few miles north of this confluence and runs from just west of Yogo Creek to just before the Judith River. It runs westsouthwest (WSW)-eastnorhteast (ENE).[17]

Mineralogy

A 0.19 carat diamond-cut cornflower blue Yogo sapphire.
A 0.37 carat brilliant-cut purple Yogo sapphire. Only about 2% of Yogo sapphires are purple.

The term "Yogo sapphire" refers only to sapphires from the Yogo Gulch.[18] About $25 million of gemstone has been recovered by all mines at Yogo.[4] At least 28 million carats are estimated to still be in the ground.[4][19] Corundum's chemical formula is Al2O3,[5] and the chemical structure of the Yogo is Al2O3 + NaAlSi3O8.[6]

The Yogo sapphire deposit is a silica-poor lamproite igneous rock dike cutting into limestone that intruded a fissure into the earth.[5] It varies from a few feet to almost 100 feet (30 m) in width, averaging 8 feet (2.4 m) wide, is over 5 miles (8.0 km) long, and at least 7,000 feet (2,100 m) deep.[7][13][20] It contains large amounts of biotite and pyroxene.[21][22] Conversely, except for one small Kashmir site and Yogo Gulch, corundum is mined from the sand and gravel created by the weathering of metamorphic rock, including sapphires found elsewhere in Montana: the Missouri River, Rock Creek, and Dry Cottonwood Creek.[3][23] Therefore, most sapphires found at Yogo Gulch must be mined from hard rock, "in situ". This, plus American labor costs, make mining Yogos fairly expensive.[4][21][22] 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 merely requires digging and selling.[24]

There had been considerable debate over the years about how deep the Yogo dike was and how many ounces of sapphire rough per ton it contained, or "ounces per ton". In the late 1970s and early 1980s Delmer L. Brown, a geological engineer and gemologist, conducted the most thorough scientific exploration of the dike ever undertaken and showed it was at least 7,000 feet (2,100 m) deep and that its ounces per ton was not consistent. Brown showed that the dike's erosion was minimal and recent. He also showed that the unique characteristics of the Yogo sapphires were due to the way they were formed. Most sapphires are formed under low pressure and temperature over geologically short periods of time. This is what results in most non-Yogo sapphires having imperfections and inconsistent coloring. Conversely, characteristics of the Yogos show crystalline formation over very high temperatures and pressures over geologically long periods of time. These conditions are only possible at great depth. Yogos were formed at great depths, at least thousands of feet, perhaps miles deep, and then carried upwards by slowing thickening magma. As sapphires are heavier then magma, the smaller roughs rose closer to the surface. This is why the Yogos found to date are generally small. Mining at the English Mine confirmed this as the deeper the digging there got, the more likely miners were to find bigger Yogo roughs. Brown also showed that distribution of gem rough through the dike was not consistent, so using an average "ounces per ton" was misleading. What came to be known as the American Mine was built at a part of the dike with significantly lower "ounces per ton" than the English Mine. As a result of Brown's findings, operations at the American Mine were permanently shut down.[25]

A 0.25 carat rectangular-cut cornflower blue Yogo sapphire.

Yogo sapphires are unique among the world's sapphires: they lack color zoning, are 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.[11] Because they are found in a lode rather than alluvial deposits of the Oriental, Australian, and other Montana sapphires, Yogos present an advantage to gemcutters: they retain a perfect or near-perfect crystalline shape, making the work of gemcutters much easier. The task of cutting these gem roughs is also made easier because of the lack of inclusions, color zoning, and cloudiness.[26] Yogos also have a trigon pattern,[6] with rhombohedral crystals, a feature which is absent from sapphires from other parts of Montana.[22][27] These rhombohedrons are almost always less than 1mm in thickness and appear like striations.[28] 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 in 1910, was 19 carats in size, and was cut into an 8 carat gem.[9] Yogos tend to be 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.[1][4][27][29] 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.[7][9][30]

Montana sapphires

Sapphires were first found in the United States on May 5, 1865 by Ed Collins along the Missouri River the Missouri River in Lewis and Clark County, Montana.[18] They also have been found in several other parts of central and western and Montana and are collectively referred to as "Montana sapphires." Corundum was also found at Dry Cottonwood Creek near Butte in 1889, Rock Creek near Philipsburg in 1892, and at Quartz Gulch near Bozeman in 1894.[10][31] 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.[32]

Mining history

File:JakeHoover1894.png
Jake Hoover at age 45 in 1894. Photo taken in Lewistown for his wedding.

During the Montana Gold Rush of 1878, about one thousand men came to Yogo Creek as a result of a gold strike and the mining camp of Yogo City flourished for about three years; however, before long, few people were left. At that time, Yogo Creek was one of the gold-bearing streams in Montana that had not been actively mined. Although gold had first been discovered there in 1866, the early prospectors were chased off by local Native Americans.[8][33]

Only bits of gold and "blue pebbles" were found. It was not until late 1895 when someone finally thought 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 City for appraisal by gemologist Dr. George Frederick Kunz, the most reknowned American gemologist of the time.[34][35] Impressed by their quality and color, Kunz pronounced them “the finest precious gemstones ever found in the United States".[36][37] Tiffany's sent Hoover a check for $3,750 along with a letter that described the blue pebbles as “sapphires of unusual quality.” In February 1896, sheepherder Jim Ettien found the sapphire mother lode, the Yogo dike, while following a line of gopher holes. He sold it to Hoover.[6][38][39] Hoover in turn sold his interest in his eight original mining stakes, known as the "New Mine Sapphire Syndicate," to his two partners for $5,000.[19][36] For several years prior to discovering Yogo sapphires, Hoover had a ranch in Pig-Eye Basin. Afterwards he prospected for gold in Alaska and was a deep-sea fishing guide in Seattle, before eventually returning to the Judith Basin.[33][40]

On July 4, 1896, two other Americans, John Burke and Pat Sweeney, staked mining claims at six sections of western portion of the Yogo dike; areas Hoover had deemed unfit for mining. These claims were known as the "Fourth of July Claim". That mine became known as the "American Mine", bought in 1904 by the American Gem Syndicate and purchased in 1907 by the American Sapphire Company.[36][41]

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.[42] Millie became known as a superb cook at the English Mine, but by 1903 she had fallen on hard times. She remained there until she died in 1906, was considered Yogo City's most prominent citizen, and ultimately the last resident of the city.[42][43] Yogo City also was briefly known as Hoover City,[44] after Jake Hoover, who employed and remained lifelong friends with western painter Charles Marion Russell.[45] Russell stated he learned most of his frontier skills from Hoover.[10][46] 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 all depicted in the painting.[47][48][49][50]

File:Yogo1ct.jpg
A one-carat Yogo sapphire.
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.

In 1899, gem merchants Johnson, Walker and Tolhurst, Ltd. of London paid $100,000 for the New Mine Sapphire Syndicate, which then became unofficially known as the "English Mine."[51] This site was 5 miles (8.0 km) from Yogo City.[36] One of the Englishmen who came to the area was Charles Gadsden of Berkhamsted. By 1900, there was little left of the gold mine, though 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.[52] Weight-for-weight rough sapphires are worth much more than gold, and Gadsden's security measures were very tight.[53] The English Mine flourished until the 1920s.[20][38][51] Floods so severely damaged the mines on July 26, 1923 that they never fully recovered.[11] The "English Mine" finally succumbed to the aftermath of the floods and hard economic times in 1929.[54] It 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.[20][33][38][51]

Operations at the English Mine were significantly more profitable than at the American Mine, largely because of the mining and management techniques employed, insufficient space and water for ore weathering at their end of the Yogo dike, and inability to market the gems within the United States. Roughs from the English Mine were shipped to London and sold in Europe, often as sapphires from the Far East. The American Sapphire Company, which used less skilled gemcutters from Great Falls, Montana, went bankrupt in 1909 and a new form, the Yogo American Sapphire Company bought the American Mine but went bankrupt in 1913. The American Mine was then bought by New Mine Sapphire Syndicate in 1914, which quickly recouped its purchase price by washing the tailings left behind by the American Mine.[36][55][56] Sapphire mining at the other Montana sapphire mines was even less successful because of the very low profit margin in sapphires that are not blue. Blue sapphires are extremely rare at Montana sites other than Yogo Gulch.[33][57]

Millie Ringold, circa 1900. The structure in the background is a waterwheel that was used to power a crusher at Yogo City's Weatherwax Mine.

Other Montana sapphires were heavily mined during World War II for industrial uses. However, because the Yogo mines were still owned by the British, they were little affected by the war. Hoover remained caretaker of the mines until shortly before his death on March 11, 1954. For much of the 1930s and 1940s he was the sole employee of the mine and spent $29,000 of his own money to pay the mine's property taxes.[58] The sixth American company to acquire the Yogo dike was the Yogo Sapphire Mining Corporation of Billings, Montana. The firm made its initial offer in 1946 and obtained an agreement with the English in 1949. However, legal wrangling delayed the actual purchase until July 1956. The final price was $65,000 and various stock considerations. Like so many other Yogo ventures, its capital was exhausted. The Yogo Sapphire Mining Corporation then changed its name to the same as the British firm's name: New Mine Sapphire Syndicate. It became known as the "American Syndicate" to distinguish it from the previous "English Syndicate". Production was poor and mining ceased in September 1959.[59] From 1959-1963 the mine was "open" resulting in hobbyists, picknickers, and rockhounds from all over America and Canada coming to gather loose rough. The American Syndicate finally took action to stop this in 1963, with fences and threats of prosecution.[36][60] The American Syndicate had leased the mine to several operators. One of these was Siskon, Inc. of Nevada, who lost a significant amount of money. They sued and in May 1965 the Montana Supreme Court ruled in Siskon's favor. Siskon bought the mine at a sheriff's sale and in turn leased it to a group headed by Arnold Baron, who had a background in gemcutting and jewelry. Baron organized some German and Thai gemcutters and had success in marketing Yogos in America--the first time that occurred in 50 years. However, due to the difficulty in mining the hard rock site, he did not exercise his option to buy the mine and Siskon sold it in August 1968 when Herman Yaras bought it for $585.000.[61]

Yaras' firm was called Sapphire Village, Inc. Yaras was from Oxnard, California. This eventually led to what is now called Sapphire Village in early 1969, a nearby homesite development where people can gather their own sapphires through limited mining rights.[36] "Mining" on these homesites was limited to hand tools. Meanwhile, Sapphire Village, Inc. did little to mine and market sapphires and it folded. Yaras sold the mine in 1973 to Chikara Kunisaki, an Oxnard, California native and celery farmer. Kunisaki owned one of the original homes in Sapphire Village and named his firm Sapphire International Corporation. Kunisaki then made the first serious effort to mine Yogo Gulch since the early days of the English Mine. He built a modern 3,000 foot tunnel at the site of the old American Mine that became known as the "Kunisaki Tunnel". However, Sapphire International Corporation's operations were so costly that it shut down operations in fall 1976.[62]

Victor di Suvero and his firm Sapphire-Yogo Mines were next in January 1977 with a lease on the mine. Di Suvero was a native-born Italian who grew up in Tientsin, China and had been successful with a jade mine in California. Di Suvero's expertise was in marketing and he formed Sapphire Trading to cut and market the Yogos. He had novel marketing ideas but neglected the mining aspects of business. Consequently he was unable to make payments and this venture folded in fall 1979. At this point, only 4 Americans had been successful at Yogo Gulch and that was early in its mining history. At least thirteen American Yogo mining efforts had failed. Besides financial and hard rock mining difficulties, the Americans did not understand gem marketing. They generally approached the Yogos as if they were gold nuggets; not being able to see past a bag full of sapphire roughs.[63]

The American Mine hoist at Yogo mines.

Kunisaki then put his mine up for sale, asking $6 million to recup his expenses. Even though mine profits had been poor over the decades, during this time prices of precious gems were very high due to the world wide oil crises of the 1970s and early 1980s. Four individuals or groups seriously considered Kunisaki's offer. Relying heavily upon the expertise of Brown, Harry C. Bullock and J. R. Edington formed the limited partnership American Yogo Sapphire Limited, the 14th American company to work the Yogo dike. They paid the $6 million price and then raised $7.2 million in funding by October 1981. Bullock and Brown had Yogo mine experience prior to this as they had worked with di Suvero. Bullock's plan included mining, cutting, making jewelry, and marketing--the whole specturm of the business. Brown discovered he could get the best gemcutters for the best price, who were also willing to improve their skills, in Thailand. This is where American Yogo Sapphire Limited set up its network of cutters. Brown also set up a security system that was computerized, thorough, and started at the mine and included the Thai cutters. Bigger roughs were sent to American cutters, specialty cuts were done in Germany, and a few cuts were done in Hong Kong. The vast majority of cuts were done in Thailand. American Yogo Sapphire Limited secured a $5 million line of credit with Citibank. Desiring a more modern name, American Yogo Sapphire Limited changed its name to Intergem Limited in spring 1982. Intergem marketed the Yogo as the Royal American Sapphire. Their first line of jewelry appeared in late summer 1982. Intergem started by marketing the jewelry regionally in the American west and then national marketing. They also developed a system of authorized dealers. Intergem began marketing the Yogo, rather Royal American Sapphire, as the world's only guaranteed untreated sapphire--a claim which rocked the gem trade becaue by 1982 the issue of heat treating gems had become a major issue in the gem trade.[64] At that time 95% of all the world's sapphires were being heated to enhance their natural color. The Thais had taken this a step further by buying large quantities of Sri Lankan sapphires that were naturally colorless, known as geuda, and heating them to a totally artificial blue. Compounding the problem, heated gems often fade over time. Trained gemologists can detect a heated gem 95% of the time. Intergem's marketing of guaranteed untreated Yogos set them against many in the gem industry. This issue appeared as a front page story in the Wall Street Journal on August 29, 1984 in an article by Bill Richards entitled "Carats and Schticks: Sapphire Marketer Upsets The Gem Industry".[65] In its first 4 years Intergem met with success. In 1984 alone sales were over $3 million. In 1985 there was a movement in Pennsylvania to require require disclosure that a gem had been treated. Large numbers of gem professionals were visiting Yogo Gulch. However, problems were brewing.[66]

Gemcutting in Thailand

Intergem had begun planning to dig even deeper into the Yogo dike; which held more known reserves than all the world's other known sapphire deposits combined; albeit deep underground than near the surface like the other known deposits. By this time Sapphire International Corporation had been renamed to Roncor; to which Intergem had made a down payment and agreed to make semi-annual payments. Intergem also had loan and interest payments to make to Citibank. Intergem's sales were steadily increasing, but even still not enough cash was coming in and in May 1985 they missed a $250,000 payment to Roncor. Their collateral with Citibank had declined because their collateral was their own inventory and the value of gems was declining. Citibank called in its loan. Intergem had over $1 million in sales lined up for the 1985 Christmas season but could only fill a tiny portion. In summer 1986 Roncor regained full ownership even though Intergem had sold carats and jewelry worth millions of dollars.[36][67] 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.[36]

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 been deemed unsuitable. They began mining the site and named it the "Vortex Mine". The company was named Vortex Mining. The mine shaft went 280 feet (85 m) down and contained two Yogo ore-bearing veins.[68] The mine was successful for years but eventually declined and the Vortex Mine closed in 2004. The portion of the dike they had mined was an extension of the main dike. In 1992 Roncor found an 11 carat rough.[36][69]

AMAX Exploration, operating as the Yogo Sapphire Project, signed a 22-month lease with Roncor in March 1993 and had some success in the middle and eastern portions of the dike but decided not to continue after the end of its lease due to the cost of underground mining, depletion of easily accessible Yogos, and the relatively small size of Yogos currently easily accessible. During this time additional dikes were found in the area and low grade rough was found in what is known as the "Eastern Flats Dike".[36][70]

In 1995 Intergem's stock of gems began to reappear on the market because during its demise Intergem had paid its salesmen in but in sapphires. After Intergem collapsed, many of its salesmen continued to sell Yogos, especially after AMAX ceased operations. Citibank also had obtained a large stock of Yogo pieces as a result of Intergem's demise reputedly worth $3.5 million and consisting of 200,000 carats of rough, 22,000 carats of cut gems, and 2,000 pieces of jewelry. This sat in the bank's vaults until 1991 when Sofus Michelsen, director of the Center for Gemstone Evaluation and creator of the Michelsen Gemstone Index, became interested. In 1992 he and Jim Adair, a Missoula, Montana jeweler who is the world's largest retailer of Yogos, got together and by October 1994 Adair had purchased most of Yogo material Citibank had, which had been stored in 4 sealed bags, which contained a lot of dirt. Only one of the bags was truly valuable. Adair and Michelsen designed custom cutting techniques for Yogos.[71]

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.[9] As of 2011, there is also mining activity at Sapphire Village, though the Roncor mines are inactive.[1][20][36]

Tidbits

In the earliest years of Yogo sapphire mining before Yogos achieved their own reputation, Oriental sapphires were sold in Montana as Yogos while in Europe Yogos were sold as Oriental sapphires.[72] Paulding Farnham (1859-1927) used these stones to great advantage in several jewelry pieces he designed for the 1900 Exposition Universelle in Paris,[73] where Yogo sapphires received a silver medal for color and clarity.[36][74] Yogo sapphires also won a bronze medal at the 1904 Louisiana Purchase Exposition in St. Louis, Missouri.[75] 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.[9][22][29] The most elaborate piece of jewelry ever made with Yogos is the Tiffany Iris Brooch, which was made in the early 1900s and contains 120 Yogo sapphires.[76] In 1923 Mrs. Warren G. Harding was given an "all Montana" ring made from a Yogo sapphire and Montana gold. In 1952 Gadsden gave cut Yogos to President Harry Truman, his wife Bess Truman, and their daughter Margaret Truman.[30] While there is no doubt many Yogos have been sold in Europe, there is dispute about whether they are in any of the crown jewels of Europe or whether Princess Diana's engagement ring sapphire was a Yogo. This same ring was also Catherine, Duchess of Cambridge's engagement ring. That sapphire has been reported as being 9, 12, and 18 carats.[10][77][78]

See also

Notes

  1. ^ a b c "Sapphires". United States Geological Survey. Retrieved October 26, 2011.
  2. ^ Voynick 1985, p. vii
  3. ^ a b Voynick 1985, p. 193
  4. ^ a b c d e "Corundum". Department of Geological Sciences, University of Texas at Austin. 1998. Retrieved October 28, 2011.
  5. ^ a b c Voynick 1985, pp. ix–xi
  6. ^ a b c d Ward, Jane R. "Yogo Sapphires History". Yogo Paydirt. Retrieved October 29, 2011.
  7. ^ a b c d McRae, W. C. (2009). Montana. Berkeley: Avalon. p. 339. ISBN 9781598800142. Retrieved October 29, 2011. {{cite book}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  8. ^ a b Voynick 1985, p. 10
  9. ^ a b c d e Gibson, Richard I. (Summer 2011). "Yogos: Montana's "Goldilocks" Gem". Distinctly Montana. Retrieved October 29, 2011.
  10. ^ a b c d "State Gemstones Sapphire and Agate". Montana Department of Tourism. Retrieved November 6, 2011.
  11. ^ a b c Voynick 1985, pp. 31–32
  12. ^ "Field Guide, Little Belt Mountains". Science Education Resource Center, Carleton University. Retrieved October 29, 2011. Note: Click map
  13. ^ a b Weed, Walter Harvey (1900). Geography of the Little Belt Mountains, Montana. Washington, D. C.: United States Geological Survey, Government Printing Office. pp. 454–459. ISBN 9780750658560. Retrieved October 29, 2011. {{cite book}}: Unknown parameter |coautors= ignored (help)
  14. ^ Voynick 1985, pp. xii, 116
  15. ^ "Descriptions -- County Boundaries" (PDF). Montana Legislature. p. 22. Retrieved November 5, 2011.
  16. ^ "Montana Highway Map" (PDF). Montana Natural Resource Information System. Retrieved November 5, 2011.
  17. ^ Voynick 1985, p. 116
  18. ^ a b Voynick 1985, pp. 6–8
  19. ^ a b Sterrett, D. B. (1908). Mineral Resources of the United States, Calendar Year 1907, Part II Non-Metallic Products. Washington, D. C.: United States Geological Survey, Government Printing Office. pp. 816–819. Retrieved October 29, 2011.
  20. ^ a b c d "Yogo Gulch, Montana, Sapphire Mine". Mountain Lily Gems. Retrieved October 27, 2011.
  21. ^ a b Pirsson, Prof. L. V. (1897). Kuna, Edward S. (ed.). "Corundum-bearing Rock From Yogo Gulch, Montana". American Journal of Science. 4. 4. New Haven, CT: Yale University Department of Geology and Geophysics: 421–423. Retrieved October 29, 2011. {{cite journal}}: |chapter= ignored (help)
  22. ^ a b c d O'Donoghue, Michael (2006). Gems: Their Sources, Descriptions and Identification. Oxford: Butterworth-Heinemann. pp. 123, 144–146. ISBN 9780750658560. Retrieved October 29, 2011.
  23. ^ "Montana Sapphires - Gemology". Gem Gallery. Retrieved October 29, 2011. Note: Includes map of major Montana sapphire mines
  24. ^ Voynick 1985, pp. viii, 2–3
  25. ^ Voynick 1985, pp. 151–158
  26. ^ Voynick 1985, pp. 62–63
  27. ^ a b Kunz, Dr. George F. (1897). Kuna, Edward S. (ed.). "Sapphires From Montana, With Special Reference to Those From Yogo Gulch in Fergus County". American Journal of Science. 4. 4. New Haven, CT: Yale University Department of Geology and Geophysics: 417–420. Retrieved October 29, 2011. {{cite journal}}: |chapter= ignored (help)
  28. ^ Pratt, Dr. J. H. (1897). Kuna, Edward S. (ed.). "Crystalography of Montana Sapphires". American Journal of Science. 4. 4. New Haven, CT: Yale University Department of Geology and Geophysics: 424–428. Retrieved October 29, 2011. {{cite journal}}: |chapter= ignored (help)
  29. ^ a b Elliott, Thomas B. (May 02, 2011). "Montana Sapphire Vs. Yogo Sapphire". Jewelers Ethics Association News. 3 (8). Jewelers Ethics Association. Retrieved October 29, 2011. {{cite journal}}: Check date values in: |date= (help)
  30. ^ a b Voynick 1985, p. 204
  31. ^ Voynick 1985, pp. 19–21
  32. ^ Voynick 1985, pp. 16–19
  33. ^ a b c d "Abandoned Mines Historic Context". Montana Department of Environmental Quality. Retrieved November 6, 2011.
  34. ^ "Welcome To Montana Gem". Montana Gem. Retrieved October 25, 2011.
  35. ^ Voynick 1985, pp. 3–4, 29–31
  36. ^ a b c d e f g h i j k l m "Yogo Sapphires - History". Gem Gallery. Retrieved October 29, 2011.
  37. ^ Voynick 1985, p. 31, 29-31
  38. ^ a b c Moser, Cathy (Spring/Summer 2009). "Yogo City or Bust". Big Sky Journal. Bozeman, MT. Retrieved October 24, 2011. {{cite journal}}: Check date values in: |date= (help)
  39. ^ Voynick 1985, pp. 32–35
  40. ^ Voynick 1985, pp. 109–112
  41. ^ Voynick 1985, pp. 74–76
  42. ^ a b Voynick 1985, p. 21
  43. ^ "Ringold, Millie (1845-1906)". Black Past. Retrieved November 2, 2011.
  44. ^ Taliaferro, John (1996). Charles M. Russell: The Life and Legend of America's Cowboy Artist (2003 ed.). Norman, OK: University of Oklahoma Press. pp. 34, 40. ISBN 0-8061-3495-X. Retrieved October 31, 2011. {{cite book}}: Invalid |ref=harv (help)
  45. ^ Paladin, Vivian A. "Facts and Reflections About Charles M. Russell". Art Montana. Retrieved November 6, 2011.
  46. ^ Voynick 1985, pp. 22–30
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  48. ^ "Yogo Sapphires". Russell Country. Retrieved October 31, 2011.
  49. ^ Boggs, Johnny D. (September 25, 2009). "Following Charlie Russell's Paintbrush". True West Magazine. Retrieved November 2, 2011.
  50. ^ "Utica (A Quiet Day in Utica) By Charles M. Russell". Sid Richardson Museum. Retrieved November 2, 2011.
  51. ^ a b c Voynick 1985, pp. 36–42
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  53. ^ Voynick 1985, pp. 80–81
  54. ^ Voynick 1985, pp. 102–109
  55. ^ Voynick 1985, pp. 57–64
  56. ^ Voynick 1985, pp. 75–77, 95–96
  57. ^ Voynick 1985, pp. 76–78
  58. ^ Voynick 1985, pp. 119–130
  59. ^ Voynick 1985, pp. 125–134
  60. ^ Voynick 1985, pp. 134–135
  61. ^ Voynick 1985, pp. 136–138
  62. ^ Voynick 1985, pp. 138–144
  63. ^ Voynick 1985, pp. 144–150
  64. ^ Voynick 1985, pp. 151–154, 158–164
  65. ^ Voynick 1985, pp. 165–181
  66. ^ Voynick 1985, pp. 181–185
  67. ^ Voynick 1985, pp. 185–191
  68. ^ Voynick 1985, pp. 193–195
  69. ^ Voynick 1985, pp. 196–198
  70. ^ Voynick 1985, pp. 198–201
  71. ^ Voynick 1985, pp. 201–207
  72. ^ Voynick 1985, pp. 62–64
  73. ^ Zapata, Janet (1991). "The Rediscovery of Paulding Farnham, Tiffany's Designer Extraordinaire, Part I: Jewelry". Antiques. 139 (3). Brant Publications: 561. {{cite journal}}: |access-date= requires |url= (help)
  74. ^ Voynick 1985, pp. 57–58
  75. ^ Voynick 1985, p. 93
  76. ^ Voynick 1985, pp. 114–115, 204
  77. ^ Voynick 1985, p. 163
  78. ^ Wilkes, David (November 17, 2010). "A Ring Fit For His Mother...and His Love: Prince William's Sapphire and Diamond Engagement Ring for Kate". Daily News. Retrieved November 6, 2011. {{cite news}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)

References

  • Voynick, Stephen M. (1985). Yogo The Great American Sapphire (March 1995 printing, 1987 ed.). Missoula, MT: Mountain Press Publishing. ISBN 0-87842-217-X. {{cite book}}: Invalid |ref=harv (help)

External links

Wikimedia Commons has media related to Yogo mine and sapphires.
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