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Consumer Guide on Jewelry
Source: Federal Trade Commission
Buying jewelry can be fun, exciting and confusing. Whether you're considering a gift of jewelry for someone special or as a treat for yourself, take some time to learn the terms used in the industry.
A Jewelry Shopper’s Checklist
When you're in the market for a piece of jewelry for yourself or someone you
love, shop around. Compare quality, price, and service. If you're not
familiar with any jewelers in your area, ask family members, friends, and
co-workers for recommendations. You also should:
- Ask for the store's refund and return policy before you buy.
- Check for the appropriate markings on metal jewelry.
- Ask whether the pearls are natural, cultured, or imitation.
- Ask whether a gemstone is natural, laboratory-created, or imitation.
- Ask whether the gemstone has been treated. Is the change permanent? Is special care required?
- Make sure the jeweler writes on the sales receipt any information you relied on when making your purchase, such as the gem's weight or size. Some jewelers also may supply a grading report from a gemological laboratory.
In addition, these tips apply when you're shopping for jewelry online:
- Shop with companies you know or do some homework before buying to make sure a company is legitimate before doing business with it.
- Get the details about the product, as well as the merchant's refund and return policies, before you buy.
- Look for an address to write to or a phone number to call if you have a question, a problem or need help.
Gold
The word gold, used by itself,
means all gold or 24 karat (24K)
gold. Because 24K gold is soft, it's usually mixed with other metals to
increase its hardness and durability. If a piece of jewelry is not 24 karat
gold, the karat quality should accompany any claim that the item is gold.
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The karat quality marking tells you what proportion of gold is mixed with the other metals. Fourteen karat (14K) jewelry contains 14 parts of gold, mixed in throughout with 10 parts of base metal. The higher the karat rating, the higher the proportion of gold in the piece of jewelry.
Most jewelry is marked with its karat quality, although marking is not required by law. Near the karat quality mark, you should see the name or the U.S. registered trademark of the company that will stand behind the mark. The trademark may be in the form of a name, symbol or initials. If you don't see a trademark accompanying a quality mark on a piece of jewelry, look for another piece.
Solid gold refers to an item made of any karat gold, if the inside of the item is not hollow. The proportion of gold in the piece of jewelry still is determined by the karat mark.
Jewelry can be plated with gold in a variety of ways. Gold plate refers to items that are either mechanically plated, electroplated, or plated by any other means with gold to a base metal. Eventually, gold plating wears away, but how soon will depend on how often the item is worn and how thick the plating is.
Gold-filled, gold overlay and rolled gold plate are terms used to describe jewelry that has a layer of at least 10 karat gold mechanically bonded to a base metal. If the jewelry is marked with one of these terms, the term or abbreviation should follow the karat quality of the gold used (for example, 14K Gold Overlay or 12K RGP). If the layer of karat gold is less than 1/20th of the total weight of the item, any marking must state the actual percentage of karat gold, such as 1/40 14K Gold Overlay.
Gold electroplate describes jewelry that has a layer (at least .175 microns thick) of a minimum of 10 karat gold deposited on a base metal by an electrolytic process. The terms gold flashed or gold washed describe products that have an extremely thin electroplating of gold (less than .175 microns thick). This will wear away more quickly than gold plate, gold-filled or gold electroplate.
Platinum, Silver and Other Metals
Platinum is a precious metal that
costs more than gold. It usually is mixed with other similar metals, known
as the platinum group metals: iridium, palladium, ruthenium, rhodium and
osmium.
Different markings are used on platinum jewelry as compared with gold jewelry, based on the amount of pure platinum in the piece. The quality markings for platinum are based on parts per thousand. For example, the marking 900 Platinum means that 900 parts out of 1000 are pure platinum, or in other words, the item is 90% platinum and 10% other metals. The abbreviations for platinum - Plat. or Pt. - also can be used in marking jewelry.
Items that contain at least 950 parts per thousand pure platinum can be marked simply platinum. Items that have at least 850 parts per thousand pure platinum can be marked with the amount of pure platinum and the word platinum or an abbreviation (for example, 950 platinum, 900 Plat. or 850 Pt.). Jewelry that contains less than 850 parts per thousand pure platinum, but has a total of 950 parts per thousand of platinum group metals (of which at least 500 parts is pure platinum), may be marked with both the amount of pure platinum and the amount of the other platinum group metals in the piece. For example, the marking 600 Plat. 350 Irid. means that the item has 600 parts per thousand (60%) platinum, and 350 parts per thousand (35%) iridium, totaling 950 parts per thousand of platinum group metals, and 50 parts per thousand (5%) other metals.
The words silver or sterling silver describe a product that contains 92.5% silver. Silver products sometimes may be marked 925 which means that 925 parts per thousand are pure silver. Some jewelry may be described as silverplate: a layer of silver is bonded to a base metal. The mark coin silver is used for compounds that contain 90% silver. According to the law, quality-marked silver also must bear the name or a U.S. registered trademark of the company or person that will stand behind the mark.
Vermeil (ver-may), a special type of gold plated product, consists of a base of sterling silver that is coated or plated with gold.
Pewter items may be described and marked as such if they contain at least 90% tin.
Diamonds
A diamond's value is based on four criteria: color, cut, clarity, and carat.
The clarity and color of a diamond usually are graded. However, scales are
not uniform: a clarity grade of "slightly included" may represent
a different grade on one grading system versus another, depending on the
terms used in the scale. Make sure you know how a particular scale and grade
represent the color or clarity of the diamond you're considering. A diamond
can be described as "flawless" only if it has no visible surface
or internal imperfections when viewed under 10-power magnification by a
skilled diamond grader.
As with other gems, diamond weight usually is stated in carats. Diamond weight may be described in decimal or fractional parts of a carat. If the weight is given in decimal parts of a carat, the figure should be accurate to the last decimal place. For example, ".30 carat" could represent a diamond that weighs between .295 - .304 carat. Some retailers describe diamond weight in fractions and use the fraction to represent a range of weights. For example, a diamond described as 1/2 carat could weigh between .47 - .54 carat. If diamond weight is stated as fractional parts of a carat, the retailer should disclose two things: that the weight is not exact, and the reasonable range of weight for each fraction or the weight tolerance being used.
Some diamonds may be treated to improve their appearance in similar ways as other gemstones. Since these treatments improve the clarity of the diamond, some jewelers refer to them as clarity enhancement. One type of treatment - fracture filling - conceals cracks in diamonds by filling them with a foreign substance. This filling may not be permanent and jewelers should tell you if the diamond you're considering has been fracture-filled.
Another treatment - lasering - involves the use of a laser beam to improve the appearance of diamonds that have black inclusions or spots. A laser beam is aimed at the inclusion. Acid is then forced through a tiny tunnel made by the laser beam to remove the inclusion. Lasering is permanent and a laser-drilled stone does not require special care.
While a laser-drilled diamond may appear as beautiful as a comparable untreated stone, it may not be as valuable. That's because an untreated stone of the same quality is rarer and therefore more valuable. Jewelers should tell you whether the diamond you're considering has been laser-drilled.
Imitation diamonds, such as cubic zirconia, resemble diamonds in appearance but are much less costly. Certain laboratory-created gemstones, such as lab-created moissanite, also resemble diamonds and may not be adequately detected by the instruments originally used to identify cubic zirconia. Ask your jeweler if he has the current testing equipment to distinguish between diamonds and other lab-created stones.
Pearls
Natural or real
pearls are made by oysters and other mollusks. Cultured
pearls also are grown by mollusks, but with human intervention;
that is, an irritant introduced into the shells causes a pearl to grow. Imitation
pearls are man-made with glass, plastic, or organic materials.
Because natural pearls are very rare, most pearls used in jewelry are either cultured or imitation pearls. Cultured pearls, because they are made by oysters or mollusks, usually are more expensive than imitation pearls. A cultured pearl's value is largely based on its size, usually stated in millimeters, and the quality of its nacre coating, which gives it luster. Jewelers should tell you if the pearls are cultured or imitation.
Some black, bronze, gold, purple, blue and orange pearls, whether natural or cultured, occur that way in nature; some, however, are dyed through various processes. Jewelers should tell you whether the colored pearls are naturally colored, dyed or irradiated.
Gemstones
Natural gemstones are found in
nature. Laboratory-created stones,
as the name implies, are made in a laboratory. These stones, which also are
referred to as laboratory-grown, [name of manufacturer]-created, or
synthetic, have essentially the same chemical, physical and visual
properties as natural gemstones. Laboratory- created stones do not have the
rarity of naturally colored stones and they are less expensive than
naturally mined stones. By contrast, imitation
stones look like natural stones in appearance only, and may be
glass, plastic, or less costly stones. Laboratory-created and imitation
stones should be clearly identified as such.
Gemstones may be measured by weight, size, or both. The basic unit for weighing gemstones is the carat, which is equal to one-fifth (1/5th) of a gram. Carats are divided into 100 units, called points. For example, a half-carat gemstone would weigh .50 carats or 50 points. When gemstones are measured by dimensions, the size is expressed in millimeters (for example, 7x5 millimeters).
Gemstone treatments or enhancements refer to the way some gems are treated to improve their appearance or durability, or even change their color. Many gemstones are treated in some way. The effects of some treatments may lessen or change over time and some treated stones may require special care. Some enhancements also affect the value of a stone, when measured against a comparable untreated stone.
Jewelers should tell you whether the gemstone you're considering has been treated when: the treatment is not permanent; the treated stone requires special care; or the treatment significantly affects the value of the gemstone.
Some common treatments that you may be told about and their effects include:
- Heating can lighten, darken or change the color of some gems, or improve a gemstone's clarity.
- Irradiation can add more color to colored diamonds, certain other gemstones and pearls.
- Impregnating some gems with colorless oils, wax or resins makes a variety of imperfections less visible and can improve the gemstones' clarity and appearance.
- Fracture filling hides cracks or fractures in gems by injecting colorless plastic or glass into the cracks and improves the gemstones' appearance and durability.
- Diffusion treatment adds color to the surface of colorless gems; the center of the stone remains colorless.
- Dyeing adds color and improves color uniformity in some gemstones and pearls.
- Bleaching lightens and whitens some gems, including jade and pearls.
Garnet, the January birthstone, derived its name from the Latin word
granatus, meaning like a grain, which refers to the mode of occurrence
wherein crystals resemble grains or seeds embedded in the matrix. Garnet is
a family of minerals having similar physical and crystalline properties.
They all have the same general chemical formula, 
,
where A can be calcium, magnesium, ferrous iron, or manganese, and B can be
aluminum, ferric iron, or chromium, or in rare instances, titanium.
The formulas and names of common garnet species are:
Some rare species of garnet are known that illustrate the wide range of substitution that the garnet crystal structure can accommodate. They include:
There are a number of trade and variety names for garnet, most of these names are for particular colors of a specie. Hessonite is the variety name for a fine orange, cinnamon brown, or pinkish variety of grossularite, while tsavorite is the trade name for fine dark green grossularite. Melanite is a black titanium bearing variety of andradite and demantoid is a rich green variety. Malaya is a trade name for a pyrope-spessartite that varies in color from red, through shades of orange and brownish orange to peach and pink. Rhodolite is a purplish red pyrope-almandite solid solution garnet. Fine-quality pyrope garnets from Czechoslovakia are often called Bohemian garnets. Almandite and almandite-pyrope solid solution garnets are the best abrasive types, but andradite, grossularite, and pyrope also are used. All species of garnet have been used as gemstones.
Figure 4. Star garnet from Idaho.
(Photo is courtesy of the author.)
Garnet displays the greatest variety of color of any mineral, occurring in every color except blue. For example, grossularite can be colorless, white, gray, yellow, yellowish green, various shades of green, brown, pink, reddish, or black. Andradite garnet can be yellow-green, green, greenish brown, orangy yellow, brown, grayish black or black. Pyrope is commonly purplish red, purplish red, orangy red, crimson, or dark red; and almandite is deep red, brownish red, brownish black or violet-red. Spessartite garnet can be red, reddish orange, orange, yellow-brown, reddish brown, or blackish brown. A few garnets exhibit a color-change phenomenon. They are one color when viewed in natural light and another color when viewed in incandescent light.
The use of garnets as a gem or gemstone can be traced to prehistoric times. However, the first industrial use of garnet appears to have been as coated sandpaper manufactured in the United States by Henry Hudson Barton (founder of Barton Mines Corp.) in 1878. Its use has grown from that single sample of garnet coated sandpaper, to world industrial uses of more than 110,000 tons per year. In 1994, United States production of industrial garnet was valued at about $14 million, while gem garnet production was valued at only about $233,000.
Many deposits within the United States produce fine gem-quality garnets and three deposits are mined for industrial garnet. A State-by-State review is presented below.
Alaska.--Garnets from deposits along the Stikine River, often called "Wrangell garnet" after the nearest town which is located on Wrangell Island, are famous as mineral specimens because of their near perfect crystalline form. The garnets have limited use as gemstones because of their deep red color, however some cabochons are cut from them.
Arizona.--Arizona is one of five States that has commercial production of gem garnets. Arizona's gem garnet is red pyrope from two locations in the extreme northern portion of Apache County on the Navajo Indian Reservation. One location is at Garnet Ridge which is about 8 km west of the town of Mexican Water, and the other location is in Buell Park on the Arizona and New Mexico border, about 16 km north of Fort Defiance. Faceted stones cut from materials from these locations average 1/2 to 1-1/2 carats in size, but stones as large as 5 carats are known from these locations. Additionally, fine-quality andradite specimens, some suitable for cutting, are available from an area near Stanley in Graham Co.
California.--Gem- and specimen-quality white to pale green grossularite garnet occurs on Indian Creek in Siskiyou County and along Traverse Creek near Georgetown in Eldorado County. Other locations for these types of grossularites are the south side of Watts Valley in Fresno County, near Selma in Tulare County, near Big Bar in Butte County and near El Toro in Orange County. Some of the finest quality spessartite garnet known come from pegmatites in San Diego County. Spessartites have been found on Gem Hill near Mesa Grande and in mines in the Rincon and Pala Districts. The most productive area with the finest quality garnets is on the western side of Hatfield Creek Valley near Romona. Near Indian Head Hill in San Diego County is a deposit of fine-quality hessonite garnet, and another deposit is near Dos Cabezas.
Colorado.--Faceting-grade spessartite garnets can be found in the gas cavities in the rhyolite flow on Ruby Mountain near Nathrop, Chaffee County. Large specimen-grade garnets are available at the abandoned Salida Copper Mine.
Connecticut.--Garnet in mica schist near Roxbury and Roxbury Falls in Litchfield County was once mined, although not recently, for use in abrasive applications and for mineral specimens. The andradite garnet was found as well-formed dodecahedral crystals that separate easily from the host schist.
Idaho.--Alluvial deposits of almandite garnet were discovered in the early 1880's near Fernwood in Benewah County, but commercial gem and industrial mining did not start until the early 1940's. The deposits are on Emerald, Carpenter, and Meadow Creeks about 6.4 km from a mica-garnet schist formation. The garnet-bearing gravels are about 1 m to about 1.2 m thick and contain 8% to 15% garnet. These deposits are the basis of the largest industrial garnet mine in the nation and also produce gem garnet. Additionally, star garnets are produced from the placers of Purdue Creek in Latah County.
Idaho's deposits also are the only ones in the world, besides India, that produces significant amounts of star garnets. These almandite garnets are translucent, purplish-red stones that show four- or six-ray stars when cabochon cut, or are transparent, deep red stones that can be faceted. The asterism is the result of silky rutile inclusions.
Gem-quality garnets also are produced commercially from an area of the Little North Fork and North Fork of the Clearwater River in Clearwater County. They range from purplish rose-red to a highly prized "special pink." Gem-quality garnets occur at a number of other locations in Idaho and are periodically mined by hobbyists or professional collectors for the gemstone market.
Montana. -- Several alluvial deposits of almandite-pyrope garnet are located on the drainages of the Ruby River in Madison County. One such deposit, the Alder Gulch deposit, is in the alluvial fan formed where Alder Gulch joins the Ruby River Valley. The deposit contains about 40 million tons of old placer gold tailings that grade 4.5% almandite-pyrope garnet. The alluvium consists of high-energy, fluvial, well-rounded material, approximately 50% of which is +9 mm in size. The source of garnet along the Ruby River is highly metamorphosed Archean rocks in the Tobacco Root and Greenhom Mountain Ranges to the east. The garnets are present mostly as broken fragments of crystals which were originally as much as several centimeters in diameter. Some of the garnets from this industrial garnet deposit are of gem quality.
Bright red and orange red, to reddish-pink pyrope-almandite garnets are found associated with sapphires in the gravels of the Missouri River near Helena in Lewis and Clark County.
Nevada.--An alluvial deposit of almandite garnet is found along Hampton Creek Canyon in White Pine County about 3 km from the mouth of the canyon. No production history is available for the deposit. The source of the garnet is quartz-garnet-mica-staurolite schist that forms a portion of the walls of the canyon.
Spessartine garnets can be found at several locations in White Pine County. Most of the dark brown crystals are of interest only as specimen, but a few will cut very small clear stones.
New Hampshire.--A garnet deposit is located near North Wilmont in Merrimack County, where small alrnandite crystals are found in a biotite, quartz, and albite feldspar matrix. The crystals range up to about 19 mm in diameter but average only 6 to 10 mm in diameter.
New York.--Deposits of industrial garnet are found at two locations in New York. In the Gore Mountain area, industrial garnet is mined as the primary product; and near the town of Willsboro, byproduct of it is recovered as wollastonite mining.
The deposit near Gore Mountain is an almandite-bearing diorite of uncertain, igneous or metamorphic origin. The garnet is present as imperfectly developed crystals surrounded by a rim of coarsely crystalline hornblende. The crystals range from about 1 millimeter to almost 1 meter in diameter but average about 100 millimeters in diameter. The garnet has a pronounced laminated structure, which enables it to naturally break into thin plates from about 2 to 6 millimeters in thickness. Garnet fragments maintain this platy particle shape even as they are crushed smaller and smaller.
These same deposits in Warren County contain good to fine quality facet-grade garnets. The garnet is a solid solution of pyrope-almandite-grossularite that results in a pleasant deep brownish-red material which often has an orange cast. Beautiful small stones can be cut, but larger stones are too dark to be attractive.
North Carolina.--Large deposits of almandite and rhodolite garnet of gem and abrasive quality are known in Clay, Jackson, Macon, Madison, and Burke Counties. Abrasive-grade garnet was produced from some of these deposits from 1900 to about 1926, but no production has been recorded recently. The deposit of almandite garnet in Clay County is in a hornblende gneiss at Penland Bald on Buck Creek.
Fine red colored, gem-quality pyrope garnets have been found in the wastes from placer gold operations in Burke, McDowell, and Alexander Counties. Rose-pink rhodolite garnets are recovered from gravels in Cowee Creek near Franklin, and Mason's Branch near Iotla, both in Macon County. Rhodolite can be found in situ on Mason Mountain.
Pennsylvania.--Almandite garnet crystals are found in a quartzose mica schist about 1.6 km west of Chelsea in Delaware County. Near the surface the schist is badly weathered and the garnets, which comprise as much as 75% of the rock locally but average much less, are easily recovered. Abrasive-grade garnet was produced from this deposit prior to 1900, but no production has been recorded since the turn of the century.
Small trapezohedral crystals of almandite garnet are scattered through-out a badly decomposed gneiss near Chester Heights, also in Delaware County. An attempt was made to mine this deposit years ago by means of a shaft and underground workings.
Utah.--Large specimen-grade, apple-green grossularite garnets have been found in western Beaver County. Two locations southeast of Mexican Hat, San Juan County produce pyrope garnets similar to the bright red pyropes from Arizona and New Mexico.
Virginia.--A deposit of garnet is located on a steep bluff on the northeast side of the Tyle River about 6.5 km south of Arrington in Nelson County. The small, dull-red garnets are found in a sericitic schist. Attempts were made to mine the deposit in the past, but there is no record of commercial production.
Two mines in Amelia County account for the majority of the production of gem-quality garnet, they are the Morefield and Rutherford. The spessartine from these mines, primarily the Rutherford, are etched-crystal masses and fragments, not individual perfect crystals. The pieces range from pea size to as large as a grapefruit. In 1991, a single piece, dubbed the Rutherford Lady, was found that weighed more than 2,800 carats. Color varies from a fantastic light pure orange, almost yellow to shades of red-orange, red, and brownish-red, but the orange overtone always is present.
U.S. production of gem-grade garnet will continue to increase and additional deposits will be brought into production in the coming years.
Figure 5 -- Contra luz opal from Oregon.
(Photo is courtesy of Kevin Lane Smith.)
Opal is brittle, heat sensitive, and breaks and scratches easily; additionally, some varieties self- destruct through the loss of water. Even with these drawbacks, opal's unsurpassed beauty guarantees its status as a premier gemstone. The derivation of its name even adds to its position. Reportedly, opal's name evolved from the Roman word opalus from the Greek word opallios meaning "to see a change of color." The Greek word was a modification of the ancient Indian Sanskrit name for opal, upala, which meant "precious stone." If one spoke in mixed tongues, then opal would be opallios upala, "to see a change of color precious stone."
As indicated by the derivation of its name, opal has centuries of history as a treasured gemstone. Historically, beliefs associated with the wearing of opal have varied. The early Greeks thought that opals gave their owners the powers of foresight and prophecy, and the Romans adored it as a token of hope and purity. Eastern people regarded it as sacred, and Arabs believed it fell from heaven. In the nineteenth century, superstitions grew about the bad luck or fate that could befall one for wearing opal if it were not the wearer's birthstone. Today, these superstitions have diminished, but some people still believe it is bad luck to wear opals.
Opal has over one hundred variety and trade names, but the list of accepted or commonly used names is much shorter. The most important and most widely known opal is the precious opal. Precious opal may be subdivided further by color modifiers, white, black, pinks, and blue, which describe the body color of the opal. Australia is famous for its white and black precious opal. Fire opal, the bright red, reddish-yellow, orange, or brownish-red body colored opal is the second most important opal commercially. Until recently, the best fire opal came from Mexico.
Arizona.--Two commercial mining operations in Arizona produce blue precious opal. The body color is a light or pale blue with strong play of color in red, blue, green, and orange. The two operations sell most of its material as finished stones at the Tucson Gem and Mineral show and other local gem shows.
Idaho.--In Idaho, opal is the second largest contributor to the total value of gem material produced. The varieties produced include precious (white and pink), yellow, blue, pink, and common. The Spencer opal mine, the largest privately owned gem stone producer in the State, is the major producer of opal. At Spencer the precious opal occurs as one or more thin layers within common opal partially filling gas cavities within a rhyolite-obsidian flow. About 10% of the material is thick enough to cut into solid gems; the remainder is fashioned into doublets and triplets. The Spencer Mine is the source of pink common opal and pink precious opal.
Louisiana.--The reported precious opal from Louisiana is a sandstone/quartzite with precious opal cement and matrix. It has blue or purple play of color. The material could be cut into cabochons for jewelry and other items of interest. To date, most of the material has been cut into large (over 2-inches in diameter) gemstone spheres.
Nevada.--Nevada is known for precious opal from Virgin Valley. The first discovery of precious opal in the Virgin Valley area was in 1905 or 1906. Since then a significant quantity of the highly prized opal has been recovered. Virgin Valley opal is comparable to any in the world for its vivid play of color and in terms of the size of material available. Individual pieces weighing over 3 kilograms have been recovered from the Virgin Valley deposits. In 1993, miners found a 100-kilogram opalized log containing precious opal. The material varies in body color from deep pure black to brown to yellowish-white to white to colorless. The play of color includes all colors common to precious opal, red, blue, green, yellow, orange, etc. The opal occurs primarily as replacement of wood, or sometimes, as replacement of conifer cones. Some opal does occur as nodules filling void spaces in clay. The wood replacement is so complete, that generally the wood grain and banding are no longer visible. The exception to this would be that often the exterior wood texture is still present as a brown or black rind.
The uses of the opal can be restricted because of crazing. Crazing is the breakdown or deterioration of opal by the development of very fine cracks all over the surface that extend until they intersect. In the worst cases, the surface of the opal deteriorates into a crumbling sand-like material. Because of the crazing the opal is not well suited for use in jewelry, but displayed in water, glycerine, mineral oil or other liquids makes remarkably beautiful mineral specimens. The mineral collections of most of the better museums contain very fine pieces of Virgin Valley opal. Many museum pieces are crazed from exposure to the air.
During the summer months, at least two dig for fee mines in Virgin Valley are open to individuals. One mine is operated by the Hodson family and the other by the Wilson family. Individuals pay a daily fee to dig and keep all the opal that they find. Other mines in the area are commercial opal producers.
Two other locations in Nevada also have produced precious opal. The opal does not have as good a play of color as that from Virgin Valley and it has the same crazing problem. One location is south of the Virgin Valley in the Calico Mountains of Humboldt County, and the other is near Gabbs in Nye County. The three precious opal locations and many other locations around the State produce common opal and opalized wood.
Oregon.--During 1988, West Coast Gemstones, Inc., began mining and marketing a variety of very fine-quality opals from Opal Butte in Morrow County, OR. The varieties produced includes hyalite, rainbow, contra luz, hydrophane, crystal, fire, blue, and dendritic. Exquisite stones as large as 315 carats have been cut from contra luz rough from this deposit.
The deposit at Opal Butte has been known since the late 1800's. It was of interest only to hobbyists until recently because people believed most of the opal was unstable. Stability can be a problem with the opal, crazing can occur when stresses are created from shrinkage due to water loss. West Coast has developed methods of drying the opal that greatly reduce crazing. Even with the drying procedures, the stability varies from 20% to 90% depending upon the variety.
The opals are found in rhyolite geodes (thundereggs) in a perlite that has altered to a pastel colored clay. The geodes that contain gem-quality opal are only about 10% of the total geodes mined and only about 1% of the geodes contain gem-quality opal with play of color. The remaining geodes contain agate, quartz crystals, or common opal. The geodes vary greatly in size, from a few centimeters in diameter to over a meter.
The deposit continues to produce a supply of very fine quality opal for
cutting and carving. Currently, a company has launched an American gemstone
jewelry line based on the Opal Butte's opal. Plans are to operate the mine
for at least the next 5 years.
Peridot is the best known gem variety of olivine, a species name for a series of magnesium-iron rich silicate minerals. This bright yellow-green to green gemstone has caught the fancy of humans for thousands of years. Some historians even suspect that at least some of the "emeralds" worn by Cleopatra were actually peridot. Much of its recent popularity can be explained by its currently being recognized as the birthstone for the month of August, people wear the stone because it is supposed to bring the wearer success, peace, and good luck.
The United States was for many years the largest producer of peridot, the value of production in 1993 was estimated to be about $1.5 million, according to the USBM. The United States is getting major Competition from China and Pakistan for the title of world's largest producer.
The earliest recorded production of peridot was in about 70 A.D. from St. Johns Island in the Red Sea, about 54 kilometers off the coast of Egypt. Most of the earliest known peridot gems came from this location and small amounts of material are still being produced from there today. Later, very large, fine-quality peridot was produced from deposits in Myanmar (formerly Burma). These deposits were well known for their 20- to 40-carat cut stones of superb color and clarity, but since the socialist government came to power, the supply of Burmese peridot has been curtailed to such a point as to no longer be a factor in the industry. One can only guess as to whether the deposits are mined out, or if government policies have resulted in the shortage of material.
Arizona.--Currently, the United States is the basic suppler of peridot to the world gemstone industry. Deposits in Arizona are the major source of U.S. peridot. Faceted Arizona peridot is highly prized locally, but also enjoys widespread popularity for the manufacture of birthstone and other jewelry. The bright green, yellow-green to olive-green peridot is used both as a faceted and tumbled gem. The faceted stones are used in rings, earrings, pendants, bracelets, and as accent stones. The tumbled gems can be set in baroque jewelry, drilled and strung as beads, used in mosaics, and in the manufacture of gem trees.
Peridot Mesa, located on the San Carlos Apache Indian Reservation east of Globe in Gila County, is the most productive locality for peridot in the world. A second Arizona location from which peridot is recovered is Buell Park Apache County, Arizona, about 16 kilometers north of Fort Defiance. However, it is estimated that 80% to 95% of the world's production of peridot comes from the San Carlos Reservation.
The peridot occurs as individual grains and aggregates of grains in a basalt which is about 3 to 35 meters thick that forms the top and sides of Peridot Mesa. The material is recovered after it has weathered out of the basalt, in the gullies and canyons which lead down the sides of the Mesa or it is recovered in place in the basalt. The latter method of recovery requires drilling and blasting. The peridot grains that are commercially recovered are typically 6 to 13 millimeters in size. Therefore, the faceted stones produced from this material are generally about 1 carat in size; 2 to 3 carat stones are not uncommon, but stones, particularly flawless ones, 5 carats and over are unusual. Stones as large as 15 and 22 carats have been cut from San Carlos peridot.
On the Reservation, peridot can be mined only by individual Native Americans or by individual families of Native Americans from the San Carlos Reservation. In the past, the miners have not marketed the peridot directly to the gemstone industry. They marketed the material in random size lots, from as small as a coffee can full to as much as a 55-gallon barrel full, to local brokers or mineral dealers. These local brokers/dealers may or may not sort and grade the material, but they do tend to market to the industry in uniform size lots. Currently, some of the large volume miners are marketing the material directly to the industry and are also contracting for cutting services and are marketing cut stones.
New Mexico.--Gem-quality peridot can be found in deposits at three
different locations in New Mexico. The deposits are in the Buell Park area
in McKinley County in the northwestern part of the State and in Kilbourne
Hole and Potrillo Mar depression, both near the Mexican border in the
southeastern part of the State. The color of the material is brown,
greenish-brown, yellowish-green, and the desirable peridot green. Some
people believe the material from the Kilbourne Hole area is superior to the
material from the famous Arizona location on the San Carlos Reservation.
Currently, there is no commercial production of material from any of the
deposits in New Mexico, but "rockhounds" and other mineral
collectors gather materials from these locations for their own use.
Figure 9. -- Sapphire from the Missouri River in Montana.
(Photo is courtesy of Robert Weldon.)
The production of gem-quality sapphires in the United States is not new or recent. In 1865, the first U.S. sapphires were found in the gravels of the Missouri River in Lewis and Clark County, Montana. This was followed by subsequent discoveries on Dry Cottonwood Creek in Deer Lodge County in 1889, on Rock Creek in Granite County in 1892, and in Yogo Gulch in Judith Basin County in 1895. Additionally, small amounts of sapphire are recovered from Quartz Gulch in Granite County, Pole Creek in Madison County, the Missouri River in Chouteau County, and Brown's Gulch in Silver Bow County. Furthermore, corundum crystals, from which star sapphires have been cut, are found in Beaverhead and Madison Counties. Also, in 1895, the first sapphires were produced from the Cowee Valley in Macon County, North Carolina. But until very recently, with the exception of Yogo Gulch material, the commercial gemstone industry has had limited interest in U.S. sapphires.
Montana.--Mining of Yogo Gulch sapphires began within a year of their discovery in 1895 and continued for 39 years. In 1923, the mine was damaged so badly by rain that it could not economically recover. Other attempts have been made to commercially mine the deposit, but to date, all of these attempts have ended in economic failure.
Yogo's are unique among the world's sapphires. They lack the color zoning so prevalent in other sapphires, their uniform "corn-flower blue" color is natural (not the result of heat-treating), and their clarity is uniformly high. These features rank them among the world's finest sapphires. Unfortunately, the rough is both small and flat, wafer-like in shape. The majority of the crystals or pieces of crystals recovered are too small to be cut, most are less than 1 carat and finds of over 2 carats are rare. Reportedly, the largest crystal was a 19 carat stone found in 1910 that was cut into an 8-carat stone. The size of the cut stones greatly restrict the market for Yogo's, they are beautiful, small, very expensive sapphires.
Currently, Yogo sapphires are produced from three sources: Rancor lnc., produces material from the original Yogo Gulch deposit; Vortex Mining produces from a recently discovered extension of the Yogo dike; and material is produced by individuals from privately owned lots in Sapphire Village. The first two producers market only cut stones and finished goods and the third is comprised essentially of hobbyists.
Historically, the amount of sapphires produced from the Missouri River and Rock Creek areas greatly exceeded that from Yogo Gulch. However, the value of the material produced from Yogo, reported to be in excess of $30 million, is significantly greater than that of the combined values of the other areas. This relationship is rapidly changing.
The combination of large volume commercial operations on the Missouri River, and to some extent Rock Creek, plus the advent of successful heat-treating techniques for the material has greatly enhanced the acceptance of these sapphires by the gemstone industry. This enhanced acceptance has resulted in a significant increase in the market for and value of U.S. sapphires. Unconfirmed reports have circulated that a parcel of select 3- to 10-carat material, suitable for heat-treating, was sold for as much as $40,000 per kilogram. A more realistic price for 3- to 10-carat, sorted mine-run material is in the range of $5,000 per kilogram, with many kilograms of mine-run rough selling for $1,000 per kilogram.
The sapphires from the Missouri River gravels in Lewis and Clark County are a mixture of rough and pitted crystals showing well defined faces and completely rounded and smooth-surface highly stream worn pebbles. The majority of the material is pale blue or blue-green, with deep blue stones quite rare. Stones also are found in pastel blue, green, pink, pale red, purple, yellow, and orange. Most of the stones recovered are less than 6.4 millimeters in diameter, but material 6.4 to 12.7 millimeters in diameter are not uncommon. Material greater than 12.7 millimeters in diameter is rare.
Currently there are seven operations on the Missouri River that commercially produce sapphires and/or operate a dig-for-fee area. Not all of these may be active in any one year. It is the author's understanding that one operation, currently inactive, (a self-propelled floating 16-inch suction dredge) is for sale. The mines operate from about the last week of May through the first week of September.
The Rock Creek sapphires are very similar to the sapphires from the Missouri River but differ in the general shape of the crystals. The stones are basically crude hexagonal plates about the same dimension in width and height, with a much higher percentage of the material being well rounded water worn pebbles. There appears to be more of the larger sized (greater than 12.7 millimeters) material. Additionally, it is reported that the Rock Creek material has a greater percentage of stones that can be heat-treated for color enhancement.
During the past several years, there has been only a single producer on Rock Creek. The producer operated both a commercial recovery plant and a fee recovery area. The fee recovery area sold buckets of gravel for washing and also offered, for a predetermined fixed fee, the output of one day's operation of the commercial wash plant. There is work underway which would result in a second, much larger producer, opening an operation on another deposit in the area. If things go as planned, the new operation on Rock Creek would be the largest sapphire producer in Montana.
There are a number of locations between Dillon in Beaverhead County and Ennis in Madison County that produce lavender, grayish-lavender, bluish-gray, and gray hexagonal sapphire crystals that, when cut, produce stones that contain four- or six-ray stars. At least one producer from the Dillon area is currently advertising the availability of this type of material. The remainder of the sapphire deposits in Montana appear to be operated by individual hobbyists.
More should be said about the effects of heat-treating techniques on Montana sapphires, and the variety of fancy colored sapphires available. Not all Montana sapphires are suitable for heat- treating because of variations in chemical composition. Also, the sapphires from the Missouri River respond to heat-treating differently than those from Rock Creek The response to heat-treating can vary also depending upon the method (individual) used to treat the sapphires.
The yield on treatment of Missouri River sapphires is lower than for Rock Creek. It is reported that 20% to 30% of Missouri River sapphires heat-treat from deep, well saturated blue to pale, pale blue. The corresponding treatment rate for Rock Creek material is in the range of 60%. Heat-treating also yields or improves the color of fancy colored sapphires. Bright yellows and oranges are the result of heat-treating, whereas heat-treating improves the color of some pinks by removing colors that can interfere with the desirable pink shades. Montana sapphires can be diffusion treated, but because of their high iron content they are not particularly well suited for this form of enhancement.
North Carolina.--North Carolina is well known for its hobbyist production of sapphire. Sapphire have been produced from the Cowee Valley in Macon County since 1895 when the American Prospecting and Mining Co. systematically mined and washed the gravels of Cowee Creek. Today a number of dig-for-fee operations are located in the Cowee Valley. Each year many people pay to dig or purchase buckets of gravel to wash in hopes of finding a sapphire, garnets, and other gem materials. Many of the dig-for-fee operations have enriched the gravels with gem materials from other locations.
Every year articles appear in magazines and newspapers about large and
valuable sapphires found at one or more of the mines in Cowee Valley. No
doubt large corundum crystals and pieces of corundum are found each year. By
the same token, valuable sapphires may be found, but the number of large
valuable gemstones are far less than reported, and the values are generally
not as great as reported. During the period when the area was commercially
mined, gem material was found that would cut fine quality 3- to 4-carat
stones, but the amount of quality gem material available has greatly
declined. It is doubtful that North Carolina will ever again boast of
commercial sapphire production, or that the commercial gemstone industry
will seriously consider the State's sapphire deposits.
Tourmaline seems to have a special place in the hearts of mineral collectors as well as in that of gem and gemstone enthusiasts. Its nearly universal popularity is based on two very important facts: first, it is a bright and beautiful gemstone that can be found in just about any color; and second, materials that are of acceptable quality are affordable to most purchasers.
The word "rainbow" is used figuratively to describe tourmaline. In reality, it is a well recognized fact that tourmaline's diversity in color is not limited to the seven colors of the rainbow. Tourmaline can be colorless to just about any color, hue, or tone known to man. And if range of colors among different tourmalines is not enough, individual crystals can vary in color along their length or in cross-section.
The variations in color along a crystal's length give rise to the bicolor and tricolor tourmalines which have multitudes of color combinations. The variation in color in cross-section can be concentric, as in the case of "watermelon" tourmaline, a pink core surrounded by a green rind. Or the variation may have a distinct triangular pattern as in the case of liddicoatite.
California.--Tourmaline was, until recently, the single largest contributor to the value of gemstones produced from California. And for the past 5 years, California has ranked as high as second and as low as sixth in the value of natural gemstone produced in the United States. The State's fabulous tourmalines were discovered by the gemstone industry in the late 1870's or early 1880's. The caveat, discovery by the gemstone industry, is used because Native Americans discovered and used these beautiful tourmalines long before that.
Since their discovery, the tourmaline deposits in Riverside and San Diego Counties have had more tourmaline produced and of greater value than any other deposits in the Northern Hemisphere. In fact, it is probable that only the deposits in Brazil have been more productive.
One of the reasons for the productivity of the area is the longevity of the individual mines. Many of them have operated intermittently from the 1890's until the present. The famous Himalaya Mine is quite likely the best example.
Records indicate that from 1898 until 1914, the Himalaya was the world's largest producer of tourmaline. Furthermore, the records indicate that in 1904 production from the mine was at least 5.5 metric tons. In 1989, 84 years later, a single pocket in the mine produced more than 0.5 metric ton of tourmaline.
The history of production from the mine is not one of steady continuous operation. The mine operated continuously from 1898 until 1914, after which it operated sporadically until 1952. At this time, it once again began continuous operations that lasted until 1964 when it returned to intermittent operation until 1977. Since then the mine has been in operation under the direction of Pala International.
California tourmalines come in all colors except certain shades of blue and yellow. They also occur in bicolors, tricolors, and concentrically and laterally zoned combinations. Crystals vary in diameter from about 3 millimeters to as much as 125 millimeters, and vary in length from about 12 millimeters to as much as 250 millimeters.
Because of the large size of the crystals available, some large stones have been cut from California tourmaline. A 400-carat pink-red stone has been cut, as well as a flawless 75 carat green to pink bicolor and flawless 30- to 40 carat green to colorless to pink tricolored stones.
California deposits should continue to produce quantities of faceting, carving, and cabochon grade, as well as specimen-grade tourmalines for some time into the future. In late 1992, a new deposit of tourmaline was discovered in Riverside County that could result in greater production over even a longer period of time.
Maine.--Tourmaline was the first gemstone mined in the United States by miners other than prehistoric man or Native Americans. Tourmaline mining began at Mount Mica, ME, in 1822 and, with starts and stops, has continued to the present. In 1992, operations at Mount Mica produced both gem-quality and mineral specimen tourmaline.
Figure 11.--Tourmaline from Maine.
(Photo is courtesy of Smithsonian.)
Over the years, mining operations on Mount Mica produced hundreds of kilograms of tourmaline. Museums and private collections around the world contain outstanding examples of tourmaline from the deposit. The largest reported crystal from the site apparently is one that is 39.4 centimeters long, 17.8 centimeters wide, and weighs about 14.3 kilograms. Apparently, a flawless, blue-green 256-carat stone is the largest cut stone from Mount Mica.
Mount Mica may have been the first tourmaline producer in Maine, but it is by no means the largest. Newry Hill, a spur off Plumbago Mountain, or more specifically the Dunton Mine on Newry Hill, is the most prolific tourmaline producer in Maine. Since its discovery in 1898, production from the mine has exceeded thousands of kilograms of high-quality tourmaline. The mines ability to yield large quantities of quality tourmaline was clearly demonstrated by Plumbago Mining Corp. The company reported that from October 1972 until the Fall of 1974, it produced more than one metric ton of fine-quality tourmaline.
Other mines and quarries in a three county area produce gem- and specimen-grade tourmalines. The level and type of activities at each mine or quarry vary from year to year. Currently, most of them are open to hobbyist or professional collectors for a fee or with the owners permission.
Maine tourmalines come in a wide variation of colors, deep grass green to
light green to yellow-green to blue green. They are also found in all shades
of red, from pink to deep red, and blue-green to light blue to deep blue,
and as colorless crystals. The State's mines also produce bicolors and
watermelon crystals. The colors can be very fine and some believe that Maine
tourmalines set the standard for non-chrome green tourmaline.
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