Yogo sapphire

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Yogo sapphire
A 0.65-carat (0.13 g) AAA quality cornflower blue Yogo sapphire
A 0.65-carat (0.13 g) AAA quality cornflower blue Yogo sapphire
General
Category Oxide mineral
Chemical formula Aluminium oxide, Al2O3
Identification
Color Cornflower blue to purple
Crystal habit Hexagonal, rhombohedral, prismatic or dipyramidal
Crystal system Hexagonal
Symbol (32/m)
Space group R3c
Twinning Lamellar
Cleavage Partings on {0001} and {1011}
Fracture Uneven to conchoidal
Tenacity Brittle
Mohs scale hardness 9.0
Luster Adamantine to vitreous
Specific gravity 3.98–4.10
Optical properties Uniaxial (–) Abbe number 72.2
Refractive index nω=1.767–1.772
nε=1.759–1.763,
Birefringence 0.008
Pleochroism Weak
2V angle 58°
References [1]

Yogo sapphires are a variety of corundum found only in Yogo Gulch, located in central Montana in the Little Belt Mountains in Judith Basin County, Montana on land once inhabited by the Piegan Blackfeet people. Yogos are typically cornflower blue in color, a result of trace amounts of iron and titanium. Gemologists consider them among the finest sapphires in the world. They have high uniform clarity and maintain their brilliance under artificial light. However, because Yogo sapphires occur within a hard igneous dike that is very deep and has a vertical dip, mining efforts have been sporadic and rarely profitable. It is estimated that at least 28,000,000 carats (5,600 kg) carats of Yogos are still in the ground.

More gem-quality sapphires are produced in Montana than anywhere else in North America. Today, the term "Montana sapphire" generally refers to gems found in Montana locations other than Yogo Gulch, where "Yogo sapphire" is the preferred term for the gems found there. Sapphires were first discovered in Montana in 1865, in alluvium along the Missouri River. Finds in other locations in the western half of the state occurred in 1889, 1892, and 1894. The Rock Creek location, near Phillipsburg, Montana is the most productive site in Montana, and its gems inspired the name of the nearby Sapphire Mountains. In 1969, the sapphire was co-designated along with the agate as Montana's state gemstone.

Yogo sapphires were not immediately recognized and valued. Gold was discovered at Yogo Creek in 1866, and though "blue pebbles" were noticed alongside gold in the stream alluvium by 1878, it was not until 1894 that the "blue pebbles" were recognized as sapphires. Sapphire mining began in 1895 after a local rancher named Jake Hoover sent a cigar box of gems he had collected to an assay office, which in turn sent them to Tiffany's in New York, where an appraiser pronounced them "the finest precious gemstones ever found in the United States".[2] Hoover purchased the original mother lode from a sheepherder and in turn sold it to other investors. It became highly profitable English Mine, which flourished from 1899 until the late 1920s and, under a series of changing owners, periodically operated into the early 21st century. A second operation, the "American Mine," was owned by a series of investors in the western section of the Yogo dike, but was less profitable and ultimately bought out by the syndicate which owned the English Mine. In 1984, a third set of claims, known as the Vortex mine, opened.

In the early 1980s, Intergem Limited, who controlled most of the Yogo mining at the time, rocked the gem world by marketing Yogos as the "Royal American Sapphire," promoting it as the world's only guaranteed "untreated" sapphire, exposing a practice of the time wherein 95 percent of all the world's sapphires were heat-treated to enhance their natural color. Although Intergem ultimately went out of business, the gems it mined appeared on the market well into the 1990s because during its financial demise, the company had paid its salesmen in sapphires. Citibank also had obtained a large stock of Yogos as a result of Intergem's collapse, and after keeping them in a vault for nearly a decade, sold its collection in 1994 to a Montana jeweler.

At the 1900 Exposition Universelle in Paris, Yogo sapphires received a silver medal for color and clarity. They won a bronze medal at the 1904 Louisiana Purchase Exposition in St. Louis, Missouri. Jewelry containing the gems was given to First Ladies Florence Harding and Bess Truman and many gems were sold in Europe, although promoter's claims that Yogos are in the crown jewels of England or the engagement ring of Princess Diana are unlikely. Today, a number of Yogo sapphires are part of the Smithsonian Institution's gem collection.

Contents

[edit] Location

Yogo Gulch is located in Montana
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Yogo Gulch
Yogo Gulch, Montana

Yogo sapphires are mined in Montana at Yogo Gulch (46°50′45″N 110°18′38″W / 46.84583°N 110.31056°W / 46.84583; -110.31056 (Yogo Creek)),[3] which is in Judith Basin County, Montana, 12 miles (19 km) southwest (SW) of Utica, 45 miles (72 km) west-southwest (WSW) of Lewistown, and east of Great Falls.[4][5][6] At the time Yogo sapphires were discovered, the site was in Fergus County. However, in 1920, the Montana county boundaries were redesigned, and Judith Basin County was created from part of western Fergus County and eastern Cascade County.[7][8]

Yogo Gulch and the corresponding natural features of Yogo Peak (8,625 feet (2,629 m)), Yogo Creek, and the Yogo dike, where the gems are mined, are all located in the Little Belt Mountains within Judith Basin County.[6] The Gulch is located along the lower reaches of Yogo Creek and west of the Judith River. The westernmost end of the Yogo dike occurs just west of Yogo Creek, about 3 miles (4.8 km) north of Yogo Creek's confluence with the Middle Fork of the Judith River, from that point it runs east-northeast (ENE) and ends about 0.5 miles (0.80 km) before reaching the Judith River.[9] Yogo Creek starts just south of Yogo Peak, which is about 15 miles (24 km) west of the Judith River. From there the creek flows southeast (SE) into the Middle Fork of the Judith River.[9] The Judith River then flows northeast (NE) from the Little Belts toward Utica. East of the Judith River is Pig-Eye Basin, where Jake Hoover, discoverer of Yogo sapphires, owned a ranch.[10]

[edit] Etymology

Yogo Gulch lies in a region historically inhabited by the Piegan Blackfeet people. The meaning of the word "Yogo" had been lost by 1878 when placer gold was found in Yogo Creek, and hence its meaning is uncertain. However, promoters of Yogo sapphires claim that word yogo may mean "romance" or "blue sky" in the Blackfoot language.[11][12] Other meanings for yogo have been suggested, including "Going over the hill".[13]

[edit] Mineralogy and geology

Sapphires are a form of corundum, a crystalline form of aluminium oxide (Al2O3).[14] Corundum is one of the hardest minerals, rating 9 on the Mohs scale.[15][16] Corundum gems of most colors are called sapphires, except for red, which are called rubies.[17] The term "Yogo sapphire" refers only to sapphires from the Yogo Gulch.[18] The cornflower blue color of the Yogo results from trace amounts of iron and titanium.[11] Yogo sapphires are unique in that they lack color zoning, are free of cavities and inclusions, have high uniform clarity, and do not need heat treating because their cornflower blue coloring is uniform and deep.[19] Unlike Asian sapphires, they maintain their brilliance in artificial light.[20] Yogos present an advantage to gemcutters:[21] since they are found as primary constituent minerals within an igneous bedrock rather than in sedimentary alluvial deposits where most other sapphires are located,[19] they retain a perfect or near perfect crystalline shape, making cutting much easier, as does their lack of inclusions, color zoning, or cloudiness.[21] Yogos also exhibit a triangular pattern on the basal plane of the flattened crystals,[15] with thin rhombohedral crystal faces, a feature absent in sapphires from other parts of Montana.[22][23][24]

A 0.37-carat (0.074 g) brilliant cut purple Yogo sapphire. Only about two percent of Yogo sapphires are purple.
A 0.43-carat (0.086 g) pear-shaped cornflower blue Yogo sapphire

Yogos tend to be beautiful, small, and very expensive.[25] The United States Geological Survey and many gem experts have stated that Yogos are "among the world's finest sapphires."[26][27][28] The roughs tend to be small and flat, so cut Yogo gems heavier than 2 carats (0.40 g) are rare.[26] Only about 10 percent of cut pieces are over 1 carat (0.20 g).[19] The largest recorded Yogo rough, found in 1910, weighed 19 carats (3.8 g) and was cut into an 8-carat (1.6 g) gem.[26] The largest cut Yogo is 10.2-carat (2.0 g).[11][29][30] Because of the rarity of large rough Yogo sapphires, gem prices begin rising sharply when they are over 0.5 carats (0.10 g), and skyrocket when they are over 1 carat (0.20 g).[22][25][29]

Montana sapphires in general come in a variety of colors,[17][19][23] but Yogos are almost always blue, possibly because their host rock had a longer cooling time, allowing a more even distribution of titanium and iron throughout the stone's crystals.[29] About two percent of Yogos are purple, rather than blue.[19]

Yogo sapphires were first discovered in alluvium during gold mining operations in Yogo Gulch, but were later traced to their source within the Yogo dike.[31] Except for the Yogo Gulch deposit and one small site in Kashmir, most other corundum is alluvial, mined from the sand and gravel created by the weathering of metamorphic rock. Alluvial sapphires are found in the Orient, Australia, and in three other Montana locations—the Missouri River, Rock Creek, and Dry Cottonwood Creek.[32][33] The location of most Yogo sapphires within hard igneous rock rather than from alluvial placer deposits, coupled with American labor costs, makes their extraction fairly expensive.[17][22][34] At least 28,000,000 carats (5,600 kg) are estimated to still be in the ground.[17][35]

The host rock for the sapphires, the Yogo dike, is a dark gray to green lamprophyre consisting of clinopyroxene and phlogopite phenocrysts set in a matrix of clinopyroxene, titanian magnetite, apatite, chlorite, serpentine and calcite. The phlogopite composition suggests a 900 °C (1,650 °F) crystallization temperature. Xenoliths of limestone, clastic sedimentary rocks, and gneiss are present. In some locations, due to the abundance of xenoliths, the dike has the appearance of a limestone breccia in an igneous matrix.[31] One gneiss fragment found as a xenolith contains corundum. The Yogo sapphires themselves are rimmed with a reaction layer of spinel and are etched, indicating that the sapphires were not in chemical equilibrium with their host, the lamprophyre magma. This suggests the sapphire crystals may have originated in an earlier rock, such as a corundum-bearing gneiss, later assimilated by the lamprophyre magma at depth.[31][36] Earlier investigators had assumed that the sapphire had crystallized from the magma with the necessary high aluminium content provided by assimilation of clay rich shales of the Proterozoic Belt Supergroup sediments which are known to be present at depth in the region.[34]

The Yogo dike is a narrow, near vertical sheet-like igneous intrusion. It varies from 2 to 26 feet (0.61 to 7.9 m) thick and extends for 5 miles (8.0 km) forming a linear feature across the landscape with a compass direction or strike of 75° east of north. This linear body is broken into three offset en echelon segments.[31] It has been dated at 48.6 mya using Ar dating on phlogopite. The dike intrudes Mississippian age (360 to 325 Mya) limestone and other sedimentary rocks of the Madison and Big Snowy Groups.[31]

There was considerable debate over the years as to the depth of the Yogo dike and how many ounces of rough sapphires per ton it contained. In the late 1970s and early 1980s, Delmer L. Brown, a geological engineer and gemologist, conducted the most thorough scientific exploration to date, concluding that the dike was at least 7,000 feet (2,100 m) deep and that the concentration of rough sapphires was not constant throughout the deposit.[37] Brown found that the dike had intruded into a pre-existing fault that had been a conduit for groundwater circulation. The overlying shale, the Kibbey Formation, was deposited on an unconformity, an ancient Mississippian age karst erosion surface,[38] and was not intruded by the dike.[37] This groundwater action had produced collapsed zones which were intruded by the dike to form breccia zones. Recent erosion in the area removed the overlying shales and again exposed the limestone to groundwater action which again produced collapse breccias which include fragments of the dike rock. He determined that the erosion of the dike in the current erosion cycle was minimal. Brown also showed that the unique characteristics of the Yogo sapphires are related to their geological history. Most sapphires are formed under low pressure and temperature over geologically short periods of time, and this is why most non-Yogo sapphires have imperfections and inconsistent coloring.[37] Yogos show crystalline formation under very high temperatures and pressures over geologically long periods of time, conditions only possible at great depths: Yogos were formed at depths of thousands of feet, perhaps miles deep, and then carried upwards by slowly thickening magma. As sapphires are heavier than magma, the smaller roughs rose closer to the surface,[37] which was later confirmed by subsequent mining at the English Mine. Brown also showed that distribution of gem rough through the dike was not consistent, so using an average "ounces per ton" was misleading. For example, the section which, despite several ownership and name changes over the years, is generally known as the "American Mine," was developed in an area dominated by "post–dike breccia" with significantly lower "ounces per ton" than the English Mine.[37]

[edit] Montana sapphires

An uncut/rough yellow sapphire found at the Spokane Sapphire Mine near Helena, Montana

The term "Montana sapphire" generally refers to gems from Montana in locations other than Yogo Gulch, where "Yogo sapphire" is the preferred term.[19] More gem-quality sapphires are produced in Montana than anywhere else in North America.[19] Other than the Yogos, all other Montana sapphires come from alluvial deposits.[19][33] Montana sapphires come in a variety of colors, though rubies are rare.[17][19][23]

The first sapphires found in the United States were discovered on May 5, 1865 along the Missouri River about 14 miles (23 km) east of Helena, Montana in Lewis and Clark County, Montana by Ed "Sapphire" Collins.[18][19] Collins sent the sapphires to Tiffany's in New York City, and to Amsterdam for evaluation;[39] however, the sapphires he sent were of poor coloring and low overall quality, garnering little notice and giving Montana sapphires a poor reputation.[40] Corundum was also found at Dry Cottonwood Creek near Butte in 1889, Rock Creek near Philipsburg in 1892, and Quartz Gulch near Bozeman in 1894.[32][19][41] By 1890, the English-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 because of fraudulent practices by the owners.[42]

Sapphires from these three sites are routinely heat-treated to enhance color.[19] While millions of carats of sapphires have been mined from the Missouri River deposits, there has been little activity there since the 1990s because of the high cost of recovery and environmental concerns. Production at Dry Cottonwood Creek has been sporadic and low-yielding. The Rock Creek area, also known as Gem Mountain, continues to be the most productive site in Montana, even more so than Yogo Gulch, producing over 190,000,000 carats (38,000,000 g) of sapphires since its inception in 1906.[19] Other Montana sapphire mines were 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.[43][44]

These gems inspired the names of features: the mountains near Rock Creek are known as the Sapphire Mountains. Garnets are also found at some Montana sapphire sites, inspiring the name of the Garnet Range, which lies to the north of the Sapphire Mountains.[45]

[edit] History

Yogo Gulch miners cleaning a sluice box
Jake Hoover's wedding photo in 1894 at age 45, in Lewistown, MT.

Mining of Yogo sapphires is exceptionally difficult and remains sporadic. Even so, Yogo sapphire mining turned out to be more valuable than several gold strikes.[46]

[edit] Discovery

Gold was first discovered at Yogo Creek in 1866, but early prospectors were chased away by local Native Americans.[43][13] During the Montana Gold Rush of 1878, about a thousand miners came to Yogo Creek, which was one of the gold-bearing streams in Montana not yet actively mined. The mining camp at Yogo City flourished for about three years, but only bits of gold and "blue pebbles" were found.[13] Eventually the population dwindled to only a few people.[13] Gold miners were not terribly interested in gems. Though sapphires by weight are more valuable than gold, they require sophisticated marketing. Few Yogos were in the streambed alluvium, and hard rock mining was needed to obtain commercial quantities. Gold was easier to mine and sell.[46] Nonetheless, sapphire mining at Yogo Gulch began when someone finally investigated the nature of the "blue pebbles" that had been noticed since 1894 along with gold in the streambed alluvium.[20][31] One story credits a local school teacher for recognizing the blue pebbles as sapphires.[47] In 1895, Jake Hoover sent a cigar box containing those he had collected while mining gold to an assay office, which in turn sent them via regular, uninsured mail to Tiffany's in New York City for appraisal by Dr. George Frederick Kunz,[19] the leading American gemologist of the time.[48] Impressed by their quality and color, Kunz pronounced them "the finest precious gemstones ever found in the United States".[2] Tiffany's sent Hoover a check for $3,750,[49] along with a letter that described the blue pebbles as "sapphires of unusual quality."[31]

Jake Hoover was credited as the discoverer of Yogo sapphires. For several years, Hoover had a ranch in Pig-Eye Basin. Hoover later prospected for gold in Alaska and was a deep-sea fishing guide in Seattle, before eventually returning to the Judith Basin.[43][50] Yogo City also was briefly known as Hoover City,[51] after Jake Hoover.

[edit] Early mining

Yogos were ultimately traced from the alluvium to their source.[31] In February 1896, sheepherder Jim Ettien found the Yogo dike, the sapphire mother lode, while following a line of gopher holes. He sold it to Hoover.[15][49][52] 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.[35] In 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".[53] This site was 5 miles (8.0 km) from Yogo City.[54]

Millie Ringold, c. 1900. Behind her is a waterwheel used at the Weatherwax Mine.

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 collectively known as the "Fourth of July Claim," which was later known as the "American Mine". In 1904 the mine was bought by the American Gem Syndicate, and it sold in 1907 to the American Sapphire Company.[55]

A prominent long-term local resident was Millie Ringold, a former slave born in 1845.[56] She had settled in Fort Benton, Montana after having worked as a nurse and servant for an army general. Ringold sold her boarding house in Fort Benton and left for the Yogo gold fields, setting up a hotel, restaurant, and saloon in Yogo City where she sang and played music.[56] Gold mining was on the decline, though Ringold was still working gold claims.[54] She also became known as a superb cook at the English Mine, but by 1903 had fallen on hard times. She remained in the area until she died in 1906, and was ultimately the last resident of the community.[56][57]

Among other local residents was a young cowhand hired by Hoover, who became the western painter C.M. Russell, and remained lifelong friends with Hoover.[58] Russell stated that he learned most of his frontier skills from Hoover.[41][59] The nearby town of Utica was featured in Russell's 1907 painting A Quiet Day In Utica,[60][61] which was originally known as Tinning a Dog. Hoover, Ringold, store owner Charles Lehman, and Russell himself are all depicted in the painting, placed between the hitching post and door of the general store.[61][62][63]

A Quiet Day In Utica by C.M. Russell

One of the Englishmen who came to the area was Charles Gadsden of Berkhamsted. By 1902, Gadsden was promoted to resident supervisor of the English Mine, and he quickly turned the mine's focus from gold to sapphires.[54] Gadsden's security measures were very tight, as weight-for-weight, rough sapphires are worth much more than gold.[64] The English Mine flourished until the 1920s,[49][53] but floods so severely damaged the mines on July 26, 1923 that they never fully recovered.[65] Between the aftermath of flooding and hard economic times, the English Mine finally failed in 1929.[65] It had recovered more than 16,000,000 carats (3,200,000 g) of rough sapphires that produced 2,500,000 carats (500,000 g) of finished gems valued at $25 million.[17][19] A series of other firms mined sapphires there, but with marginal success.[43][49][53] For much of the 1930s and 1940s Gadsden was the sole employee of the mine and used his own money to pay its property taxes.[66]

The American Mine operations were less profitable than those of the English Mine. While the English Mine used superior mining and management techniques on a richer lode, the American Mine suffered from insufficient space and lack of water for ore weathering. Roughs from the English Mine were shipped to London and sold in Europe, often with claims they were sapphires from the Far East, while the American Mine had difficulty marketing its gems within the United States. The American Sapphire Company, which used less skilled gemcutters from Great Falls, Montana, went bankrupt in 1909; a new firm, the Yogo American Sapphire Company, bought the American Mine, but was bankrupt by 1913. Gadsen and his wife convinced the New Mine Sapphire Syndicate to buy out the Yogo American Sapphire Company in 1914, and in doing so, the English syndicate gained control of all known Yogo deposits. They quickly recouped the purchase price by washing the tailings left behind by previous operators of the American Mine.[67][68]

[edit] 1940s–1970s

Montana sapphires were heavily mined during World War II for industrial abrasive and cutting purposes. However, because the Yogo mines were still owned by the English, the United States government could not control the mines, so the mines were little affected by the war, even though industrial sapphires were critical to the war effort. Gadsden remained caretaker of the mines until shortly before his death on March 11, 1954.[69] The Yogo Sapphire Mining Corporation of Billings, Montana was the next company to try to run the English Mine. They made an initial offer in 1946, and a deal had been reached by 1949. However, the purchase was not complete until 1956 because of assorted legal issues. The sale was finally completed for $65,000 cash and some stock considerations. Similar to the previous Yogo ventures, the company's capital was exhausted. The Yogo Sapphire Mining Corporation then changed its name to be the same as the former English firm's name: New Mine Sapphire Syndicate. It became informally known as the "American Syndicate" to distinguish it from the previous "English Syndicate." Production was poor and mining ceased in September 1959.[70] From 1959 to 1963 the mine itself was left unattended and unsecured, resulting in hobbyists, picnickers, and rockhounds from all over the US and Canada coming to gather loose rough sapphires. The American Syndicate took action to stop this in 1963, with fences and threats of prosecution.[71] The American Syndicate tried leasing the mine to several operators. One of these was Siskon, Inc. of Nevada, who lost a significant amount of money.[72] They sued, and in May 1965 the Montana Supreme Court ruled in Siskon's favor.[73] 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 German and Thai gemcutters and had success in marketing Yogos in America—the first time that occurred in 50 years. But due to the difficulty mining the hard rock site, he did not exercise his option to buy the mine, and Siskon sold it in August 1968 to Herman Yaras of Oxnard, California for $585,000.[72]

Yaras named his venture Sapphire Village, Inc. and in 1969 created the Sapphire Village, a nearby homesite development offering buyers limited mining rights to gather their own sapphires with hand tools. Doing no significant mining or marketing, Sapphire Village, Inc. was sold in 1973 to one of its investors, Chikara Kunisaki, a celery farmer from Oxnard, California. Kunisaki renamed the business Sapphire International Corporation and actually attempted mining. He built a modern 3,000-foot (910 m) tunnel at the site of the old American Mine, named the "Kunisaki Tunnel". But operation costs were so high that Sapphire International Corporation shut down in late 1976.[74] This was the last attempt to mine the American Mine section of the Yogo dike, and today, only the locked portal to the tunnel still exists.[75]

In January 1977, Victor di Suvero and his firm Sapphire-Yogo Mines became next to tackle 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: he formed a company called Sapphire Trading to cut and market the Yogos. He had novel marketing ideas but was not as knowledgeable about the mining side of the business. Unable to make payments, his venture folded in late 1979.[{sfn|Voynick|1985|pp=144–150}}

By 1980, only four Americans had been successful at Yogo Gulch, all early in its mining history.[{sfn|Voynick|1985|pp=144–150}} The English syndicate had been the most successful of any venture, and even its success was short-lived.[53] At least thirteen American-owned Yogo mining efforts had failed. Besides difficulties with financing and the challenges of hard rock mining, the American owners generally did not understand gem marketing.[{sfn|Voynick|1985|pp=144–150}}

[edit] 1980s and beyond

Hoist at the American Mine

Kunisaki put his mine up for sale, asking $6 million in total to recoup his expenses. Even though mine profits had been poor over the decades, prices of precious gems were very high at the time due to the worldwide oil crises of the 1970s and early 1980s. Four individuals or groups seriously considered Kunisaki's offer.[76] Relying heavily upon Delmer Brown's expertise, Harry C. Bullock and J. R. Edington formed the limited partnership American Yogo Sapphire Limited, becoming the 14th American company to work the Yogo dike. Bullock and Brown had Yogo mine experience, as they had worked with di Suvero. Bullock's plan included mining, cutting, making jewelry, and marketing—the whole spectrum of the business. They paid the $6 million asked by Kunisaki and then raised another $7.2 million in funding by October 1981. Brown located quality gemcutters in Thailand who were willing to further improve their skills, and set up the American Yogo Sapphire Company there. Brown also set up a thorough, computerized security system that tracked gems from the mine to the Thai gemcutters.[76] Bigger roughs were sent to American cutters, specialty cuts were done in Germany, a few cuts were done in Hong Kong, and the vast majority were done in Thailand.[77] 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 early 1982. Intergem marketed the Yogo as the "Royal American Sapphire." Their first line of jewelry appeared in mid-1982, first marketed regionally in the American west and later at the national level. Intergem also developed a system of authorized dealers.[76] Intergem found success in its first four years, with sales over $3 million in 1984 alone.[78]

Gemcutting in Thailand

Intergem rocked the gem trade by marketing the Yogo as the world's only guaranteed untreated sapphire. By 1982, the practice of routinely heat treating gems had become a major issue in the industry.[76] At the time, 95 percent of all the world's sapphires were being heated to enhance their natural color. The Thais had even purchased large quantities of naturally colorless Sri Lankan sapphires, known as geuda, and heated them to an artificial blue.[79] A problem with the practice was that heated gems often fade over time, though trained gemologists can detect a heated gem with 95 percent accuracy. 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".[79] In 1985 there was a movement in Pennsylvania to require disclosure that a gem had been treated. Intergem's strategy resulted in large numbers of gem professionals visiting Yogo Gulch.[78]

Intergem began 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 rather than near the surface in the manner of the other known deposits.[80] They also set up a washing plant and maintenance sheds at the site of the former American mine.[75] However, finances were a problem. Intergem had made a $1.5 million down payment and agreed to make semi-annual payments to Kunisaki's Sapphire International Corporation, which had been renamed to Roncor. Intergem also had loan and interest payments on the $7.2 million loan to make to Citibank. While the company's sales were steadily increasing, their profits were still too low and in May 1985 they missed a $250,000 payment to Roncor. Simultaneously, their collateral with Citibank, which was their gem inventory, had declined because the value of gems was declining; as a result, 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 because they did not have enough operating capital to manufacture the Yogo jewelry. In mid-1986 Roncor regained full ownership even though Intergem had sold loose gems and jewelry worth millions of dollars.[80]

Various companies attempted leasing the mine from Roncor, but in the meantime, two local couples, Lanny and Joy Perry and Chuck and Marie Ridgeway, 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", forming a company named Vortex Mining. The mine shaft went 280 feet (85 m) down and contained two Yogo ore-bearing veins.[81] The portion of the dike they had mined was an extension of the main dike.[82] The Vortex mine, renamed Yogo Creek Mining,[19] was successful for years but eventually declined and closed in 2004. [82]

A 0.19-carat (0.038 g) diamond cut cornflower blue Yogo sapphire

In 1992, Roncor found an 11-carat (2.2 g) rough.[82] 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; it 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 then easily accessible. During this time additional dikes were found in the area using geophysical magnetometer surveys. Low-grade sapphire rough was found in the Eastern Flats Dike, a parallel dike some 500 feet northeast of the main dike.[83] A Canadian company called Pacific Cascade Sapphires had a mining lease with Roncor in 2000 and 2001 but ran out of funds before becoming successful and their option expired. By this time most of the easily accessible Yogos had been mined and miners were having to dig deeper, further increasing costs.[19]

In 1995 Intergem's stock of gems began to reappear on the market because, during its financial demise, the company had paid its salesmen 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, reputedly worth $3.5 million, as a result of Intergem's collapse: 200,000 carats (40,000 g) of rough, 22,000 carats (4,400 g) 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 Citibank's four sealed bags of Yogo material. However, only one of the bags was truly valuable. Adair and Michelsen designed custom cutting techniques for Yogos.[84]

A new owner, Michael Duane Roberts, bought the Vortex mine in 2008. Its operations were designed to be environmentally friendly, using methods such as recycling all water and not using other chemicals.[29] Roberts died in a mining accident in 2012.[85] As of 2011, there was also mining activity at Sapphire Village, though the Roncor mines remained inactive.[26]

[edit] State gem of Montana

The sapphire became one of Montana's two official state gemstones in 1969. Although "Sapphire" Collins recognized as early as 1865 that the blue pebbles he found at the Missouri River were valuable, he was unable to convince bankers, merchants, or gem dealers of their value because of the poor quality of his specimens. The discovery of Yogo sapphires at Yogo Gulch in 1895 spurred investment in sapphire mines across the state, by wealthy people and firms from the eastern United States and the United Kingdom. When designation of a state gemstone was considered, the Montana Council of Rock and Mineral Clubs supported two nominees: sapphires and, due to their great abundance, Montana agates. Ultimately, these gems were jointly declared the state gemstones.[41][86]

[edit] Notable specimens

Large blue Yogo sapphire in the head of the Conchita Sapphire Butterfly, created in 2007 and currently held by the Smithsonian Institution

There are several Yogo sapphires kept at the Smithsonian Institution. The earliest donations were noted in the museum's annual report on June 30, 1899, when the institution reported that Dr. L. T. Chamberlain gave them two cut Yogos and 21 other sapphires for their Dr. Isaac Lea gem and mineral collection.[87] The record-setting 10.2-carat (2.0 g) cut Yogo is also held by the Smithsonian.[11][29][30] In 2006, gemologist Robert Kane of Fine Gems International in Helena, Montana, which today has the largest selection of Montana sapphires in the world, donated 333 Montana sapphires, weighing a total of 27.07 carats (5.41 g), to the Smithsonian's Gem and Mineral Collection, along with 98.48 grams of 18K yellow gold.[88][89] A representative of the Smithsonian asked Paula Crevoshay, a jewelry designer from Albuquerque, New Mexico, to create a piece of finished jewelry from these gems.[90][89] Crevoshay felt that a butterfly motif would best represent America's natural beauty, honor her mother's love of butterflies, and display the wide range of colors found in Montana sapphires. Crevoshay named the brooch "Conchita" in honor of her mother. It is also referred to as the "Sapphire Butterfly Brooch", "Conchita Sapphire Butterfly", and the "Montana Butterfly Brooch". Two of the sapphires used are cabochon cut and the rest are brilliant cut.[90] The majority are from the Rock Creek deposit. The largest one, however, is a blue Yogo used for the butterfly's head. Other sapphires used included gems that were yellow, purple, pink, and orange. Crevoshay and Kane presented the finished brooch to Smithsonian curator Jeffrey Post on May 7, 2007 in Washington, DC.[91] Crevoshay completed the brooch and donated it to the Smithsonian in 2007.[90]

In the earliest years of Yogo sapphire mining, before Yogos achieved their own reputation, Oriental sapphires were sold in Montana with claims they were Yogos, while in Europe, Yogos were sold with claims of being Oriental sapphires.[92] However, they became notable in their own right. Paulding Farnham (1859–1927) used them in several jewelry pieces he designed for the 1900 Exposition Universelle in Paris,[93] where Yogo sapphires received a silver medal for color and clarity.[94] An entry of uncut loose Yogo sapphires also won a bronze medal at the 1904 Louisiana Purchase Exposition in St. Louis, Missouri.[95] Farnham was the creator of the most elaborate piece of jewelry ever made with Yogos, the Tiffany Iris Brooch, which contains 120 Yogo sapphires,[96] and sold on March 17, 1900 for $6,906.84.[97] In 1923, First Lady Florence Harding was given an "all Montana" ring made from a Yogo sapphire and Montana gold. Then in 1952 Gadsden gave cut Yogos to President Harry Truman, his wife Bess, and their daughter Margaret.[30] There is no doubt many Yogos were also sold in Europe, as Yogo mining at times was conducted by British interests.[29] Yogos may have been in the personal collections of some members of the British royal family in the 1910s,[29] but promotional claims that Yogos are in any of the crown jewels of England cannot be conclusively proven or disproven.[29][41][98] Claims that that the gem in the engagement ring of Lady Diana Spencer and Kate Middleton is a Yogo are dubious, as that gem is thought to be of Sri Lankan origin, and its size indicates it is unlikely to be a Yogo.[99] That sapphire is large, most often reported as being 9 carats (1.8 g) in size, though it has also been described as 12 carats (2.4 g) and even 18 carats (3.6 g), though the latter number is the carat weight of the gold setting.[100] The claim that the gem is a Yogo can be traced to a 1984 Los Angeles Times story that described the ring as a 9-carat (1.8 g) sapphire, and quoted Intergem president Dennis Brown as saying the gem may have come from a British-owned Yogo mine.[101]

[edit] See also

[edit] Notes

  1. ^ Anthony, John W.; Bideaux, Richard A.; Bladh, Kenneth W.; Nichols, Monte C. "Corundum" (PDF). Handbook of Mineralogy. 3. Chantilly, VA: Mineralogical Society of America. ISBN 978-0-9622097-2-7. http://rruff.geo.arizona.edu/doclib/hom/corundum.pdf. Retrieved December 5, 2011.  Note: sapphire is a color variety of corundum.
  2. ^ a b Voynick 1985, pp. 29–31.
  3. ^ "Yogo Creek, near Yogo Gulch". Geographic Names Information System, U.S. Geological Survey. http://geonames.usgs.gov/pls/gnispublic/f?p=gnispq:3:::NO::P3_FID:793614. Retrieved April 25, 2012. 
  4. ^ "Field Guide, Little Belt Mountains". Science Education Resource Center, Carleton University. http://serc.carleton.edu/research_education/mtroadlogs/logs/TRGS-1991-Alkalic-1.html. Retrieved October 29, 2011.  Note: Click map.
  5. ^ Weed, Walter Harvey; Pirsson, Louise Valentine (1900). Geography of the Little Belt Mountains, Montana. Washington, DC: United States Geological Survey, Government Printing Office. pp. 454–459. http://books.google.com/books?id=dLwNAAAAYAAJ&pg=PA502. Retrieved October 29, 2011. 
  6. ^ a b Voynick 1985, pp. xii, 116.
  7. ^ "Descriptions – County Boundaries" (PDF). Montana Legislature. p. 22. http://leg.mt.gov/content/Laws%20and%20Constitution/MCA%20Supplements/description_of_county_boundaries.pdf. Retrieved November 5, 2011. 
  8. ^ "Montana Highway Map" (PDF). Montana Natural Resource Information System. http://nris.mt.gov/gis/gisdatalib/downloads/hwymapmdt.pdf. Retrieved November 5, 2011. 
  9. ^ a b Voynick 1985, p. 116.
  10. ^ Voynick 1985, pp. 15, 116.
  11. ^ a b c d McRae, W. C.; Judy, Jewell (2009). Montana. Berkeley, CA: Avalon. p. 339. ISBN 978-1-59880-014-2. http://books.google.com/books?id=Qw5nQNCOG6sC&pg=PA339. Retrieved October 29, 2011. 
  12. ^ "Yogo Sapphire Jewelery". Montana Russell Country. http://russell.visitmt.com/listings/11300.htm. Retrieved December 3, 2011. 
  13. ^ a b c d Voynick 1985, pp. 10–11.
  14. ^ Voynick 1985, pp. ix–xi.
  15. ^ a b c Ward, Jane R.; Attaway, Nancy L. "Yogo Sapphires". Attaway Gems. http://www.attawaygems.com/NMFG/yogo_sapphires.html. Retrieved December 5, 2011. 
  16. ^ Read, Peter G. (2005). Gemmology (3 ed.). Oxford: Elsevier Ltd. pp. 49–51. ISBN 0750664495. http://books.google.com/?id=t-OQO3Wk-JsC&pg=PA49&lpg=PA49&dq=corundum+mohs+9#v=onepage&q=corundum%20mohs%209&f=false. Retrieved April 22, 2012. 
  17. ^ a b c d e f "Corundum". Department of Geological Sciences, University of Texas at Austin. 1998. http://www.geo.utexas.edu/courses/347k/redesign/gem_notes/corundum/corundum_main.htm. Retrieved October 28, 2011. 
  18. ^ a b Voynick 1985, pp. 6–8.
  19. ^ a b c d e f g h i j k l m n o p q Kane, Robert E. (January/February 2003). "The Sapphires of Montana – A Rainbow of Colors". Gem Market News (Glenview, IL: Gem World International) 22 (1): 1–8.  Revised January 2004.
  20. ^ a b Voynick 1985, pp. 31–32.
  21. ^ a b Voynick 1985, pp. 62–63.
  22. ^ a b c Hughes, Richard W. (2006). Gems: Their Sources, Descriptions and Identification (6 ed.). Oxford: Butterworth-Heinemann. pp. 123, 144–146. ISBN 978-0-7506-5856-0. http://books.google.com/books?id=ZwcM5H-wHNoC&pg=PA145. Retrieved October 29, 2011. 
  23. ^ a b c Kunz, George F. (December 1897). Kuna, Edward S. ed. "Article 44: On the Sapphires From Montana, with special reference to those from Yogo Gulch in Fergus County". American Journal of Science. 4 (New Haven, CT: Yale University Department of Geology and Geophysics) 4 (24): 417–420. doi:10.2475/ajs.s4-4.24.417. http://books.google.com/books?id=j7MEAAAAYAAJ&pg=PA417. Retrieved October 29, 2011. 
  24. ^ Pratt, J. H. (1897). Kuna, Edward S. ed. "Article 46: On the crystallography of the Montana Sapphires". American Journal of Science. 4 (New Haven, CT: Yale University Department of Geology and Geophysics) 4 (24): 424–428. doi:10.2475/ajs.s4-4.24.424. http://books.google.com/books?id=j7MEAAAAYAAJ&pg=PA421. 
  25. ^ a b Elliott, Thomas B. (May 2, 2011). "Montana Sapphire Vs. Yogo Sapphire". Jewelers Ethics Association News (Washington (state): Jewelers Ethics Association) 3 (8). http://www.jewelersethicsassociation.com/docs/JEA%20News_Color%20Change%20and%20Montana%20Sapphire.html. Retrieved October 29, 2011. 
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  27. ^ Voynick 1985, p. 193.
  28. ^ Voynick 1985, p. vii.
  29. ^ a b c d e f g h Gibson, Richard I. (Summer 2011). "Yogos: Montana's 'Goldilocks' Gem". Distinctly Montana (Bozeman, MT: Star Ridge Publishing LLC). http://www.distinctlymontana.com/article/yogos-montanas-goldilocks-gem. Retrieved October 29, 2011. 
  30. ^ a b c Voynick 1985, p. 204.
  31. ^ a b c d e f g h Harlan, Stephen S. (1996). "Timing of Emplacement of the Sapphire-Bearing Yogo Dike, Little Belt Mountains, Montana" (PDF). Economic Geology (Littleton, CO: Society of Economic Geologists via George Mason University Academic Research System) 91 (6): 1159–1162. doi:10.2113/gsecongeo.91.6.1159. http://mason.gmu.edu/~sharlan/Harlan_1996_Yogo_Sapphire_Dike_Econ_Geol.pdf. Retrieved December 17, 2011. 
  32. ^ a b Voynick 1985, pp. 19–21.
  33. ^ a b "Montana Sapphires – Gemology". Gem Gallery. http://www.gemgallery.com/#montana_sapphire_gemology. Retrieved October 29, 2011.  Note: Includes map of major Montana sapphire mines.
  34. ^ a b Pirsson, L. V. (1897). Kuna, Edward S. ed. "Article 45: On the Corundum-bearing Rock From Yogo Gulch, Montana". American Journal of Science. 4 (New Haven, CT: Yale University Department of Geology and Geophysics) 4 (24): 421–423. doi:10.2475/ajs.s4-4.24.421. http://books.google.com/books?id=j7MEAAAAYAAJ&pg=PA421. Retrieved October 29, 2011. 
  35. ^ a b Sterrett, D. B. (1908). Mineral Resources of the United States, Calendar Year 1907, Part II Non-Metallic Products. Washington, DC: United States Geological Survey, Government Printing Office. pp. 816–819. http://books.google.com/books?id=YOlGAQAAIAAJ&pg=PA816. Retrieved October 29, 2011. 
  36. ^ Meyer, Henry O. A.; Mitchell, Roger H. (1988). "Sapphire-Bearing Ultramafic Lamprophyre from Yogo, Montana: A Ouachitite" (PDF). Canadian Mineralogist (Vancouver, BC: Mineralogical Association of Canada) 26: 81–88. http://rruff.geo.arizona.edu/doclib/cm/vol26/CM26_81.pdf. Retrieved December 19, 2011. 
  37. ^ a b c d e Voynick 1985, pp. 151–158.
  38. ^ Roberts, Albert E. (1979). Paleotectonic Investigations of the Mississippian System in the United States: Part One: Northern Rocky Mountains and Adjacent Plains Region. Washington, DC: United States Geological Survey, Government Printing Office. p. 225. http://books.google.com/books?id=8r1UAAAAYAAJ&printsec=frontcover#v=onepage&q&f=false. 
  39. ^ Clabaugh, Stephen E. (1952). "Corundum Deposits of Montana" (PDF). Geological Survey Bulletin 983. United States Geological Survey. http://pubs.usgs.gov/bul/0983/report.pdf. Retrieved April 23, 2012. 
  40. ^ Ward, Jane R.; Attaway, Nancy L. "Roberts Yogo Sapphire Gems". Roberts Yogo Sapphire Mines. http://www.yogogems.com/yogo_history/yogo_history.html. Retrieved November 25, 2011. 
  41. ^ a b c d "State Gemstones Sapphire and Agate". Montana Office of Tourism. http://montanakids.com/facts_and_figures/state_symbols/State_Gemstones_Sapphire_and_Agate.htm. Retrieved November 6, 2011. 
  42. ^ Voynick 1985, pp. 16–19.
  43. ^ a b c d "Abandoned Mines Historic Context". Montana Department of Environmental Quality. http://deq.mt.gov/abandonedmines/linkdocs/92tech.mcpx. Retrieved November 6, 2011. 
  44. ^ Voynick 1985, pp. 76–78.
  45. ^ Topographic Recreational Map of Western Montana. Canon City, CO: Western GeoGraphics. 1990. p. 339. ISBN 978-0-528-92551-1. 
  46. ^ a b Voynick 1985, pp. viii, 2–3.
  47. ^ "Yogo Gulch". Russell Country. 2010. http://russell.visitmt.com/listings/6795.htm. Retrieved February 9, 2012. 
  48. ^ Voynick 1985, pp. 3–4, 29–31.
  49. ^ a b c d Moser, Cathy (Spring/Summer 2009). "Yogo City or Bust". Big Sky Journal (Bozeman, MT: Jared Swanson). http://www.bigskyjournal.com/articles/big-sky-journal/spring-summer-09/67/yogo-city-or-bust.html. Retrieved October 24, 2011. 
  50. ^ Voynick 1985, pp. 109–112.
  51. ^ Taliaferro, John (1996). Charles M. Russell: The Life and Legend of America's Cowboy Artist (2003 Red River Books ed.). Norman, OK: University of Oklahoma Press. pp. 34, 40. ISBN 978-0-8061-3495-6. http://books.google.com/books?id=aAVRnON5nrMC&pg=PA40. Retrieved October 31, 2011. 
  52. ^ Voynick 1985, pp. 32–35.
  53. ^ a b c d Voynick 1985, pp. 36–42.
  54. ^ a b c Voynick 1985, pp. 71–73.
  55. ^ Voynick 1985, pp. 74–76.
  56. ^ a b c Voynick 1985, p. 21.
  57. ^ Behan, Barbara C. "Ringold, Millie (1845–1906)". Black Past. http://www.blackpast.org/?q=aaw/ringold-millie-1845-1906. Retrieved November 2, 2011. 
  58. ^ Paladin, Vivian A. "Facts and Reflections About Charles M. Russell". Art Montana. http://artmt.com/cmr/cmrbio.html. Retrieved November 6, 2011. 
  59. ^ Voynick 1985, pp. 22–30.
  60. ^ Voynick 1985, pp. 27–30, 110–113.
  61. ^ a b "Utica (A Quiet Day in Utica) By Charles M. Russell". Sid Richardson Museum. http://www.sidrichardsonmuseum.org/nu_site/collection.php/art/8. Retrieved November 2, 2011. 
  62. ^ "Yogo Sapphires". Russell Country. http://www.russellcountry.com/Yogo_Sapphires.html. Retrieved October 31, 2011. 
  63. ^ Boggs, Johnny D. (September 25, 2009). "Following Charlie Russell's Paintbrush". True West Magazine (Cave Creek, AZ: True West Publishing). http://www.truewestmagazine.com/jcontent/travel/travel/renegade-roads/2937-following-charlie-russells-paintbrush. Retrieved November 2, 2011. 
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  65. ^ a b Voynick 1985, pp. 102–109.
  66. ^ Voynick 1985, pp. 117–122.
  67. ^ Voynick 1985, pp. 57–64.
  68. ^ Voynick 1985, pp. 75–77, 95–96.
  69. ^ Voynick 1985, pp. 122–130.
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  71. ^ Voynick 1985, pp. 134–135.
  72. ^ a b Voynick 1985, pp. 136–138.
  73. ^ Siskon Corp v. New Mine Sapphire Syndicate, 145 Mont. 346, 400 P. 2d 867 (1965)
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  85. ^ "Great Falls Yogo mine owner killed in mining accident". Great Falls Tribune: p. M4. March 21, 2012. Archived from the original on April 22, 2012. http://pqasb.pqarchiver.com/greatfallstribune/access/2615282041.html?FMT=ABS&date=Mar+21%2C+2012.  (Subscription required)
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  88. ^ "Sapphire Butterfly Brooch". Smithsonian Institution. http://www.mnh.si.edu/earth/text/dynamicearth/6_0_0_geogallery/geogallery_specimen.cfm?SpecimenID=4111&categoryID=1&categoryName=Gems&browseType=name. Retrieved November 13, 2011. 
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[edit] References

  • Voynick, Stephen M. (1985). Yogo: The Great American Sapphire (March 1995 printing, 1987 ed.). Missoula, MT: Mountain Press Publishing. ISBN 978-0-87842-217-3. 

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