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Index | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z J JACINTH Jacinth is a semi-precious stone that is also known as hyacinth. it is a lustrous orange-yellow, orange-red, or yellow-brown type of zircon. Hyacinth has a hardness of 7.5 and a specific gravity of 4.65. Sometimes, topaz and grossular garnet of this color are also referred to as hyacinth (this can be very confusing). Hyacinth is mined in Sri Lanka. Even more confusing is the origin of the name, which comes from the Greek hyakinthos, which refers to blue gemstone. JADE Jade is a semi-precious stone that ranges in color from green to white to lilac to brown to almost black. Translucent jade is more highly valued than opaque jade. Jade is often cabochon set; stones with imperfections are often carved (the imperfections are simply carved away). Two different minerals are known as jade: jadeite and nephrite. Jadeite is the harder of the two; it is usually used in jewelry production. Nephrite is slightly softer and is often veined; it is used in carvings, for making beautiful bowls and vases. The Chinese have prized jade for thousands of years and regarded it as having medicinal properties when worn or ingested as a powder. Natural jadeite is called Type A or Grade A jade (waxing or wax dipping is allowed). Jadeite that had been bleached and then treated with polymers (plastic) or waxes is called Type B or Grade B jade (it is less durable than natural jade). Jadeite that had been dyed is called Type C or Grade C jade (the color is less durable than that of natural jade). Jadeite that has been both dyed and impregnated with polymers is called Type B+C or Grade B+C. JADE GLASS Jade glass is translucent green glass that is designed to imitate jade JADEITE Jadeite is the harder of the two varieties of jade. Jadeite is harder (compared to nephrite) and is usually used in jewelry production. JANETY, MARC ETIENNE The royal jeweler of King Louis XVI, Janety was commissioned to create several platinum pieces for the French monarch. The only piece known to remain is a glass-lined platinum sugar bowl dated 1786 which now finds it home in the metropolitan Museum of Art in New York City. Janety fled Paris during the French revolution only to be recalled in 1795 to fashion from platinum the standard lengths and weights for the newly established metric system. JAPANNED A Japanned finish in jewelry is when metal is finished with a lustrous, black lacquer. JASPER Jasper is a common, opaque, semi-precious stone that is found in many colors, including white, brown, yellow, red, and green. Jasper is found all over the world; it is often striped, speckled, and multi-colored. Jasper has been used for intaglio carvings. Jasper is a type of quartz belonging to the chalcedony family. It is often sealed with petroleum products. Jasper is sometimes dyed to resemble lapis lazuli and misleadingly called "Swiss lapis." Jasper has a hardness of 6.5 to 7.0. JASPERINE Jasperine refers to any type of banded jasper. JASPERIZED WOOD Jasperized wood (also called xyloid jasper) is petrified wood. It is wood that has fossilized - all the original chemicals have been replaced with minerals, making a stone-like replica of the original wood. JENSEN, GEORG Georg Jensen (1866-1935) was a Danish silversmith, ceramic artist, and sculptor. Jensen's modern-style silver jewelry is often adorned with semi-precious stones and is avidly collected. Jensen's workshop grew to have branches in Australia, New York, USA, and Toronto, Canada. JET Jet (also known as gagate) is fossilized coal. It is a hard, lightweight lustrous black stone that was used in mourning jewelry during the Victorian era (especially after Queen Victoria's husband died in 1861 and she went into long period of mourning, greatly affecting jewelry fashion). Jet is frequently cabochon cut. Most jet is from Whitby, England; jet has been mined near Whitby (on the Yorkshire coast of England) since prehistoric times. It is also found in Spain, France, Germany, and Russia, but these other sources are said to be inferior to the harder, more elastic Whitby jet. Jet has a hardness of 2.5-4 (quite soft) and a specific gravity of 1.30-1.35 (it is relatively lightweight). Jet leaves a brown streak. When burnt with a red-hot needle, jet smells like coal. Black glass and plastics are often used to imitate jet (glass is much heavier and harder than jet) - jet is warm to the touch. JEWELRY Jewelry (spelled jewellery in Britain) is articles of personal adornment, like rings, necklaces, bracelets, cuff links, and pins. Jewelry is made from metals (especially gold and silver), stones, glass, plastic, and other materials. JOB'S TEARS Job's tears (Coix lacryma-jobi) is a wild tropical grass plant that has very hard seeds. The white seeds are used as beads in jewelry. The seeds are dried, dyed or painted, polished, drilled and then strung into necklaces and bracelets. JUMP RING A jump ring is a circular metal ring with an opening. It is used to attach two other rings or links, and is then soldered or pressed shut K KARAT Abbreviated with the letter “K”, karat refers to the purity of gold, which is often alloyed with silver, nickel, copper or other metals to improve its workability and make the soft metal more durable. This is what the following marks mean: 24K = 100% pure gold 18K =18 parts gold and 6 parts alloyed metal(s) or 75% pure gold 14K = 14 parts gold and 10 parts alloyed metal(s) or 58.5% pure gold KARATCLAD Karatclad is a trademark for a very thick gold electroplating process; this type of plating is about 14 times thicker than standard electroplating. KEEPER RING A keeper ring is a ring which is used alongside another, more valuable ring to keep it securely on the finger. KING LOUIS XVI (1754-1793) Reigned over France from 1774-1792. Married to the Archduchess of Austria Marie Antoinette, he sent forces to assist the American colonies during the revolutionary war. Is quoted famously as stating that platinum was the only precious metal fit for Kings. KING CUT The king cut is a modification of the brilliant cut which is used for large diamonds. This cut has 86 facets. KNOT A knot is a flaw (a mineral inclusion) in a gemstone (usually a diamond) that is at the surface of a gem after polishing. The knot is a small raised bump on the finished gemstone. KOH-I-NUR The Koh-i-Nur (meaning "Mountain of Light") is one of the largest-known diamonds. It was found in India and belonged to the first Indian Rajahs of Malwa (in the 1300s). The gem made its way to Persia in the 1500s (taken as a spoil of war by the Mogul Sultan Babur). At some point it was returned to Indiabut was taken by the East India Company and presented to Queen Victoria of England in 1850. Tge gem was later cut and set into a brooch and later into the State Crown of the United Kingdom. The Koh-i-Nur is part of the crown jewels of England and is kept in the Tower of London, London, England. KUNZITE Kunzite is a transparent pink, light pink, or light purple gemstone that resembles roze quartz. It is a variety of the mineral spodumene. Kunzite can fade after prolonged exposure to light. Kunzite is also called "evening stone," because of its propensity to fade in bright light. The original color of some kunzite stones can be restored or even intensified by irradiation. It is usually used as a large stone and is easily chipped; small stones of kunzite are difficult to cut. Kunzite is often used in pendants. Kunzite has a hardness of 6-7 and a specific gravity of 3.1 - 3.2. Kunzite was first found in 1902 in Pala, California, USA, and is named for the gemologist George F. Kunz. Kunzite's chemical composition is LiAlSi2O6 KYANITE Kyanite is a deep sapphire blue, green, gray, or white gemstone. The color is not always uniform; it can be blotchy or in streaks. The cystals are crystals are transparent to translucent. Kyanite has a hardness of 4.5 to 6.5; the hardness varies depending on which way it is scratched (this happens because kyanite consists of long, thin crystals). It has a specific gravity of 3.58. Kyanite is found in Brazil, Burma, Kenya, Europe, India, Australia, Kenya, and the USA. Kyanite's chemical composition is Al2SiO5; it is composed of andalusite and sillimanite. L LAB RUBY (SAPPHIRE) A lab ruby (or sapphire) is a synthetic (laboratory-made) stone. It has the same composition, hardness, and specific gravity as natural rubies (or sapphires) but is much less expensive than a natural stone (since they are relatively inexpensive to create in the laboratory as comared to mining gemstones). These lab-produced stones can be legally referred to as "real" stones [as opposed to "natural" (mined) stones]. LABRADORITE Labradorite (a variety of plagioclase feldspar) is a fairly abundant grayish mineral that has brilliant flashes of color (usually green, blue or red) after it is polished (called labradorescence). The crystals are transparent to translucent. There is a darker variety of labradorite (called "black moonstone") which has bluish inclusions. Labradorite is usually cut with a flat surface in order to highlight the flashes of color. Labradorite was originally found along the coast of Labrador about 1805; it is also found in Newfoundland, other parts of Canada, also known as spectrolite, the Ukraine, the Ural mountains, and the USA. Labradorite has a hardness of 6 to 6.5 and a specific gravity of 2.70. Finnish labradorite is also known as spectrolite. LAPIDARY A lapidary is someone who cuts and polishes gemstones. LAPIS LAZULI Lapis lazuli is a rich blue opaque, semi-precious stone that has been used in jewelry since ancien times. Ground-up lapis lazuli was once used as a pigment for oil paintings. Lapis lazuli is often dyed to deepen and improve its color. Lapis has a hardness of 5.5; it chips and scratches easily. It has a specific gravity of 2.4 to 2.9. Water can dull its sheen. Lapis lazuli contains the minerals calcite (which decreases its value), pyrite (which can increase its value), and sodalite. Swiss lapis is not Lapis lazuli at all; it is dyed jasper. Denim lapis is relatively pale, low-grade, inexpensive lapis from Chile; it is the color of denim cloth because of calcite inclusions (which whiten the color and lower the value). LARIMAR Larimar is a form of pectolite (with copper) found only in a single place in the Dominican Republic. It is an opaque sky blue stone with white streaks. There are often some red to brown impurities. Larimar is usually shaped and polished (but not faceted). Larimar has a hardness of 4.5 - 6.0 and a specific gravity of 2.7 to 2.9. Larimar is not enhanced. Larimar was named for Larisa (the daughter of Miguel Mendez, a geologist who helped reintroduce this stone) and mar (the Spanish word for sea) LATHE A lathe is a machine that turns metal, wood, etc. The material to be turned is held horizontally on the machine and rotated very quickly while the jeweler applies a sharp cutting tool to the material, removing excess material, shaping the article. Rings are sometimes turned on a lathe, but most jewelers do not use lathes. LAVA Lava from the volcano Vesuvius near Pompeii in Italy has been used to make jewelry, especially cameos. Lava jewelry was popular in the nineteenth century. LAVALIER A lavalier is a pendant with a dangling stone that hangs from a necklace. Lavaliers were named for the infamous Duchess Louise de La Valliere (1644-1710), a French woman who was a mistress of the French king Louis XIV (and was involved in many intrigues at court). LEAD CRYSTAL Lead crystal is high-quality glass containing at least 10% lead oxide. Glass containing at least 24% lead oxide is called lead crystal. Glass containing at least 30% lead oxide is called full lead crystal. Lead added to the melt produces very clear glass resembling rock crystal. The process of making lead crystal was discovered by the English glassmaker George Ravenscroft in 1676. Crystal is colored by adding various metallic oxides to the melt. When cut and polished, crystal becomes quite brilliant. LEAF Metallic leaf is paper-thin sheets of metals. For example, gold, silver, platinum, and copper are rolled or pounded into metallic leaf which can be applied to surfaces. LEATHER CORD JEWELRY Jewelry strung on a thin leather cord has become popular recently. Pendants, beads, shell, feathers, and/or sharks teeth are strung on leather to make interesting necklaces and bracelets. LENTIL CUT A lentil cut stone is a cabochon cut in which the upper and lower portions of the stone are identical. LINDE STAR SAPPHIRE Linde star sapphire ("Linde stars") are synthetic star sapphires that were first made by the Linde Air Products Company in 1947 (they also developed star rubies that year). The Linde company later became a division of Union Carbide. Star sapphires are sapphires that have a six-sided asterism. LOBSTER CLAW CLASP A lobster claw clasp is a jewelry fastener that resembles the claw of a lobster. A tiny spring keeps the arm of this clasp closed. It is used to attach two other rings or links of a necklace or bracelet. LOCKET A locket is a pendant that can open up. Lockets can hold photos, hair, a charm, or other small, precious object. LONDON BLUE TOPAZ London blue topaz (Aluminum silicate fluoride hydroxide) is the darkest blue variety of topaz. Most blue topaz is silver topaz that has been irradiated and heat treated, but some stones are blue naturally. London blue topaz is found in Brazil, U.S.A., Sri Lanka, Myanmar (Burma), Russia, Australia (including Tasmania), Pakistan, Mexico, Japan, and Africa. Topaz has a hardness of 8 and a specific gravity of 3.5-3.6. LOST WAX CASTING Lost wax casting is a process of casting metal in which the original model is sculpted in wax. The wax is then enclosed in clay and the wax is melted out, making a hollow mold. The mold is then filled with molten metal. The clay is broken off and the cast metal remains. This method of casting has been used for at least 4,000 years. LOZENGE A lozenge has a diamond shape. A lozenge cut stone is a step-cut gem with a diamond shape. LUSTER A stone's luster is its sparkle or sheen - the way it reflects light. The luster depends on the nature of the stone's surface reflectivity. Some types of luster include: adamantine (also called brilliant or diamondlike, like a faceted diamond), earthy (with little reflectivity- also called dull, like shale or clay), greasy (like nepheline or apatite), metallic (also known as splendent, like pyrite or marcasite), resinous (like amber), pearly (with an iridescent reflectivity, like pearls or mica), pitchy (tarry minerals that are radioactive, like uraninite), silky (with a fibrous structure, like some tiger's eye or satin spar), vitreous (also known as glassy, like olivine, transparent quartz, or obsidian), and waxy (like halite or turquoise). A pearl's luster is derived from its nacre.
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