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 G G (IN COLOR) When grading diamonds “color” refers to the absence of color in a diamond. The rating scale begins at D (meaning colorless) and ends at Z (meaning having a lot of color). Though some color can be seen when a G diamond is graded, it appears colorless when mounted, thus it is commonly used in fine jewelry. GABLONZ Gablonz (Jablonec nad Nisou) is a city in the Czech Republic, in Bohemia, that is a center of jewelry making. Before World War 2, Gablonz was a center of high-quality glass-blowing, bead-making, and other costume-jewelry related products. GAGATE Gagate (popularly known as jet) is fossilized coal. It is a hard, lustrous black stone that was used in mourning jewelry during the Victorian era (especially after Queen Victoria's husband died and she went into a long-lasting mourning, affecting fashion). Jet is frequently cabochon cut. Gagate 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/gagate 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. GAHNOSPINEL Gahnospinel is a rare blue spinel stone that is high in zinc and magnesium. It can only be distinguished from most spinel by its high specific gravity and high refractive index. Gahnospinel has a hardness of 8, a specific gravity of 3.97. Its chemical formula is (Mg, Zn)Al2O4. GALLERY A gallery is a strip of metal that is perforated with a decorative pattern. Open galleries can be adapted by jewelers to use as a ready-made claw setting for gemstones. GARLAND STYLE Popular during the Edwardian era, this style (which includes bows, swags, and tassels) was made famous by the house of Cartier who set the delicate design in platinum. GARNET Garnets are any of a group of semi-precious silicate stones that range in color from red to green (garnets occur in all colors but blue). Some garnets used as gemstones include pyrope (the deep red garnet), almandine, spessartine, grossular, the iron-aluminum dark red garnet (also known as the carbuncle stone), Uvarovite (rare), and the lustrous Andradite (which includes the valuable green demantoid garnet, Topazolite , and Melanite). Red garnet is the birthstone for January. Garnet has a hardness of 6-8 and a specific gravity of 3.5 - 4.3. Types of Garnet: GASPEITE Gaspeite is a pale green to apple-green semi-precious gemstone that often has brown inclusions of its host rock. Gaspeite is translucent to opaque. This beautiful stone has only recently been used in jewelry, and is often set in silver. Gaspeite has a hardness of 4.5 - 5, and a specific gravity of 3.7. Gaspeite is Nickel Magnesium Iron Carbonate; its chemical formula is (Ni, Mg, Fe)CO3. This stone is found in Gaspe Peninsula, Quebec, Canada (where it was originally found and from which it derives its name) and Kambalda and Widgie Mooltha, Western Australia, Australia. GEMSTONE A gemstone (also called a precious stone) is a mineral that is valuable, rare and often beautiful. A few organic materials, like amber, coral and pearls are also considered gemstones. GEODE A geode is a rock whose crystal-filled interior can be hollow or filled. The crystals that form within the mineral crust of the geode is called druze. From the outside, geodes look like rounded, but otherwise ordinary rocks. GERMAN SILVER German silver (also know as nickel silver) is an alloy consisting of mostly copper (roughly 60 percent), and approximately 20 percent nickel, about 20 percent zinc, and sometimes about 5 percent tin (then the alloy is called alpaca). There is no silver at all in German silver. This alloy was invented around 1860 in Germany as a silver substitute. GIA GIA stands for the Gemological Institute of America. GIMMEL RING A gimmel ring is a double ring that was designed during the Renaissance. It consists of two or more interlocking rings. A gimmel ring symbolizes the union of two people. GIPSY SETTING The gipsy setting is a recessed setting in which the stone is sunk into the metal. There are often engraved designs around the stone (especially star patterns). This type of setting was developed in the late 1800's and was often used for rings. The gipsy setting is also known as the "star setting." GIRANDOLE A girandole is a kind of earring or brooch in which three pearls, stones or pendants hang from a large stone. The central drop is usually larger than the other pendants. GIRDLE The girdle is the widest perimeter of a gemstone. GIVRE BEADS Givre beads are beads made of transparent glass fused around a translucent core. Givre means frost in French. GLASS Glass is often used in jewelry, as beads (faceted or spherical), rhinestones and as poured glass. GLASS PASTE Glass paste (also known as pate de verre) is glass that is ground into a paste, put into a mold, and then melted. The final piece is an opaque, dense glass with a frosted surface. GLYPTOGRAPHY Glyptography is the art of engraving gemstones, making intaglio and cameos. Stones are engraved using grindstones with powdered emory or diamond as an abrasive GOLD Gold is a precious metal that is very soft when pure (24 Kt.). Gold is the most malleable (hammerable) and ductile (able to be made into wire) metal. Gold is alloyed (mixed with other metals, usually silver and copper) to make it less expensive and harder. The purity of gold jewelry is measured in karats. Some countries hallmark gold with a three-digit number that indicates the parts per thousand of gold. In this system, "750" means 750/1000 gold (equal to 18K); "500" means 500/1000 gold (equal to 12K). Alloyed gold comes in many colors: Karat - Percent Gold : GOLD DORE Gold dore (pronounced gold doh-ray) is a bar of semi-purified gold (e.g. bullion). After being mined, the first stage in the purification process of the gold ore produces a cast bar (gold dore) that is approximately 90% gold. The other 10% is mostly metals like silver and copper. GOLD FILLED Gold filled (abbreviated G.F. or written as "doubl? d'or") jewelry is made of a thin outer layer of gold atop a base metal. For example, jewelry marked 1/20 G.F. 12 Kt. is at least 1/20th gold and is layered with 12 karat gold. To be classified as gold-filled, a piece must be at least 1/20 gold by weight. GOLD PLATED Gold-plated metal has a very thin layer of gold on the surface, usually applied by the process of electroplating. Pieces that are gold plated are often marked G.E.P., gold electroplate, gold plated, or electro-plaque d'or. GOLD STONE Goldstone (also known as aventurine) is a shimmering quartz stone that ranges in color from yellow to red to light green to light brown. The shimmer is caused by tiny metallic particles (mica) within the stone (not gold). GOSHENITE Goshenite is the pure, colorless form of beryl (Be3AlSiO6, related to emerald and aquamarine). This hard, transparent gemstone is named for the town of Goshen, Massachusetts, where it was first found. Goshenite has been found in North and South America (especially Colombia), Northern Europe, East Africa, South Africa, and the Himalayan mountains in Asia. Goshenite has a hardness of 7.5 - 8.0 and a specific gravity of 2.6 - 2.8. It is not enhanced. Goshenite is sometimes coated with a green foil to resemble an emerald. GRADUATED A graduated necklace of beads or pearls has beads that go from a small size in the back of the neck and gradually increase in size to a maximum in the front of the necklace. GRAIN A grain is a unit of weight used for diamonds and natural pearls. Four grains are equal to one carat. GRANULATION Granulation is a method of decorating metal with tiny metallic spheres. Tiny beads of metal are soldered to the surface to form a pattern. GRAPE GARNET Grape garnets are a rare, intense violet to purple-red garnet. Grape garnets are made up of almandite and spessartite. They have a hardness of 7-7.5 and a specific gravity of 3.8 - 3.9. Grape garnets are found in the Orissa district of northwestern India. GREEN DIAMOND Green diamonds are rare, fancy diamonds and are quite valuable. Diamonds are precious, lustrous gemstones made of highly-compressed carbon; they are one of the hardest materials known. Diamonds have a hardness of 10, a specific gravity of 3.5, and a refractive index of 2.417 - 2.419 GREEN GARNET Green garnets are Demantoid garnets, a valuable green, and very lustrous type of garnet. They are a rare variety of andradite. Demantoid garnets have characteristic inclusions that look like horsetails. Demantoid garnets has a hardness of 6-7 and a specific gravity of 3.8 - 3.9. Demantoids were very popular in the 1800's, but are rarely used today. GREEN GOLD Green gold is gold that has been alloyed with a higher percentage of silver than copper. GREEN ROUGE Green rouge is chromium dioxide, which is used to polish precious metals, giving them a luster. GREENSTONE Greenstone is another name for nephrite, a semi-precious stone and a variety of jade. Nephrite is slightly softer that jadeite and is often veined; it is used in carvings, for making beautiful bowls and vases. GRELOT Grelots are small beads that have an elongated, pendant shape. GREY GOLD Grey gold is gold that has been alloyed with 15-20% iron. GRIQUALANDITE Griqualandite is tiger's eye from Griqualand, South Africa. It is a yellowish-brown to reddish-brown gemstone that has a silky luster. This gemstone has bands of yellow and brown; when viewed from the opposite direction, the colors are reversed. Tiger's eye is usually highly polished and set as a cabochon (or cut as a bead) to display the stone's chatoyancy (light reflected in thin bands within the stone). Tiger's eye is a type of chatoyant quartz with fibrous inclusions (especially crocidolite). This stone is sometimes heat-treated. Tiger's eye has a hardness of 7.0. GROSSULAR GARNET Grossular garnet is a type of garnet, calcium-aluminum silicate. Hessionite is a transparent brown, yellow, orange, or honey-colored variety of grossular garnet often used in jewelry. The yellow variety is called cinnamon stone, hyacinth or jacinth. Transvaal "jade" is a type of green to gray grossular garnet from South Africa. Pink grossular garnets varieties include landerite, rosolite, andXalostocite. Tsavorite is an emerald-green grossular garnet. Grossular garnet has a hardness of 6-7.5 and a specific gravity of 3.6. GUILLOCHE Guilloche is a type of enameling in which translucent enamel (fused glass) is applied over a metal surface that has been engraved. The Czech guilloche pin above is studded with marcasites. GUNMETAL Gunmetal is a metal alloy that is composed of 90 percent copper and 10 percent tin. GUTTA PERCHA Gutta percha is a resin from the Isonandra Gutta tree. Jewelry was made from gutta percha in the mid-1800's. Gutta percha was also used to insulate electrical cables. The Gutta percha company was founded by Dr. Montgomerie in 1845 and was in business until 1930. GYPSY RING A gypsy ring (also spelled gipsy) is a ring with a recessed stone or stones. Also known as "star setting." H H-I (IN COLOR) When grading diamonds “color” refers to the absence of color in a diamond. The rating scale begins at D (meaning colorless) and ends at Z (meaning having a lot of color). Though some color can be seen when an H-I diamond is graded, it appears colorless when mounted, thus it is commonly used in fine jewelry. HALLMARK A hallmark is an official mark (or a series of marks) made in metal that indicates the fineness of the metal and the manufacturer's mark. For example, a hallmark of 925 indicates 925 parts of gold per 1000 weight. Other hallmarks indicate the maker of the piece and sometimes the year of manufacture. In many countries (like Britain) it is illegal to hallmark metal incorrectly; some countries are notoriously lax in their enforcement of hallmark honesty. HAMMERED METAL Hammered metals have been formed, shaped, or decorated by a metalworker's hammer. The surface of hammered metal is covered with crater-like depressions made by a hammer. Many hammered metals are used in jewelry including gold, silver, brass, alumimum, etc. HARDNESS A substance's hardness is how resistant it is to being scratched. Hardness is measured using the Mohs Scale of Hardness. In the Mohs scale, one substance is harder than another if it can scratch it. For example, a diamond will scratch garnet, but not the other way around, so a diamond in harder than garnet. HAWK'S EYE Hawk's eye is a green, grey or blue variety of quartz that has parallel, fibrous inclusions of crocidolite that give it a greenish cat's eye effect (chatoyancy). This mineral has a silky luster. It looks a lot like Tiger's Eye, and often occurs with it in the same rock, but the internal structure is different. HEAT TREATMENT Heat treatment is the heating of stones to a high temperature in order to enhance the color or clarity. For example, blue-green aquamarine becomes blue with heat treatment and brown zircon becomes blue or clear. chromium .02%, and zinc .02%; the remaining 0.16 percent is sulfur, chlorine, and water. HEISHI Heishi (pronounced he-she) is jewelry made from disk-shaped beads of shell (or turquoise, lapis lazuli, and other stones). Each bead begins as a tiny flat piece of shell (or stone). A tiny stringing hole is drilled though the fragment. Many of these jagged pieces are strung together tightly on a wire and are then sanded into evenness using a fine-grained sandstone and then sandpaper. The result is a very smooth strand of disk-shaped beads. This is an ancient form of bead-making developed by the Pueblos of North America. HELENITE Helenite is a manmade (not natural) green glass that is made from "rock dust" (not volcanic ash) taken from the vicinity of the Mt. St. Helens volcano in Washington state. The dust is fired to 2700 degrees F, forming glass, which is later faceted and used as a gemstone. This glass is sometimes called emerald obsidianite or Mount St. Helens obsidian (but it is not obsidian, which is a natural glass). Helenite is sold as a souvenir of the eruption of Mt. St. Helens on May 18, 1980. The composition of rock from Mt. St. Helens is: Rock from Mt. St. Helens is composed of: silicone 60.50%, aluminum 16.60%, iron 6.02%, calcium 5.36%, sodium 4.18%, manganese 2.59%, potassium 1.20%, titanium .90%, phosphorus .35%, magnesium .12%, strontium .06%, Beryllium .04%, copper .03%, lead .03%, zirconium .02%, chromium .02%, and zinc .02%; the remaining 0.16 percent is sulfur, chlorine, and water. HELIOTROPE Heliotrope (commonly known as bloodstone) is an inexpensive type of chalcedony that is green with red highlights (caused by iron oxide). Heliotrope is porous and relatively soft. HEMALYKE Hemalyke is a synthetic hematite that is made by grinding up hematite, adding a biner (glue) and then press-molding it. The stone is sometimes faceted. Hemalyke looks very much like natural hematite - it is hard to them apart. HEMATITE Hematite (sometimes spelled hematite, and also known as kidney ore) is a lustrous, opaque, blue-black to silvery gray mineral often used in jewelry. Hematite is iron oxide (Fe2O3). Hematite has a hardness of 6.5 and a specific gravity of 4.95 to 5.16. When powdered, hematite is red; when rubbed on a hard stone, it leaves a red streak. Hematite was often used as seal stones, cut as intaglio. It is also used as beads and is faceted, carved or cut as a cabochon for use as a gemstone. The ancient Egyptians carved hematite into scarabs. Hematite is found in England, Mexico, Australia, Brazil, and the Lake Superior region of North America. HERKIMER DIAMOND Herkimer diamonds are clear, lustrous, doubly terminated crystals of quartz - they are not true diamonds. These brilliant stones are also called "Middleville Diamonds" or "Little Falls Diamonds." Herkimer diamonds have a hardness of 7. This stone is found in Middleville and Little Falls, Herkimer County, New York, USA. HESSONITE Hessonite (also called "cinnamon stone") is a cinnamon-brown to orange gemstone variety of grossular garnet. Hessonite's formula is Ca3Al2Si3O12; manganese that gives it its characteristic brown color. This transparent stone has a hardness of 6.5 - 7 and a specific gravity of 3.6. Hessonite is found in Sri Lanka, Brazil, Madagascar, Canada, and California, USA. This stone is not enhanced HOOK AND EYE CLASP A hook and eye clasp is a simple and ancient jewelry fastener that is composed of a hook and a circular piece that the hook can latch onto. It is used to attach the two ends of a necklace or bracelet. HOPE DIAMOND This famous diamond is named after Lord Henry Philip Hope who bought the diamond from a London merchant in 1830. Weighing 45.52 carats and displaying 60 plus facets, the diamond possesses a unique deep blue color. It now resides in the Smithsonian Institution after a dubious history of bringing tragedy to its previous owners. HOWLITE Howlite is a soft, white to gray mineral that takes dye very easily, and can be dyed to imitate turquoise very well (and is sometimes unscrupulously sold as turquoise). Howlite was named for its discoverer, Henry How, a Nova Scotia geologist. HYACINTH Hyacinth is a semi-precious stone that is also known as jacinth. 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. HYACINTH OPAL Hyacinth opal (also known as girasol) is a yellow or orange type of precious opal. In this opal, the play of colors seems to come from within the stone, like a floating light, and seems to follow the light source. I ICON An important and enduring symbol, often holding religious meaning. IMPERIAL JADE Imperial jade is another name for emerald jade. It is a fine emerald-green color. IMPERIAL TOPAZ Imperial topaz is golden orange-yellow topaz; it is the most valuable type of topaz. IMPERIAL MEXICAN JADE Imperial Mexican jade is not jade at all; it is calcite that has been dyed green. INCA EMERALD Inca emerald is an emerald that is mined in Equador. INCLUSION An inclusion is a particle of foreign matter contained within a mineral. Inclusions can be solid, liquid, or gaseous. Many inclusions decrease the value of a stone, but some, like rutile forming asterisms in star sapphires and needles in rutilated quartz and tourmalinated quartz, are prized. INDIAN AGATE Indian agate is another term for moss agate. INDICOLITE Indicolite is a green to blue-green variety of tourmaline. INLAY An inlay is a piece of material (often stone or glass) that is partially embedded in another material (usually metal) such that the two materials make a level surface. INTAGLIO Intaglio is a method of decoration in which a design is cut into the surface. Signet rings are frequently decorated with intaglio, as are seals. INTERGROWN Intergrown crystals occur when two mineral crystals grow together and become one. INVERALL SAPPHIRE Inverall sapphires are a type of sapphire from Inverall, New South Wales. INVESTMENT COMPOUND An investment compound is a refractory material (it can withstand extreme heat) which is slightly porous (so that gases from molten metal can escape) and can be formed into a mold (which will be used in metal casting). An example of an investment compound is plaster of paris mixed with silica, boric acid, and graphite. INVISIBLE NECKLACE An invisible (or floater) necklace looks as though the beads are simply floating on the skin; the beads or pearls are strung far apart from one another on an almost invisible string (like clear fishing line). IOLITE Iolite, also known an water sapphire, is a transparent, violet-blue, light blue, or yellow-gray mineral. Iolite is pleochroic; a single stone will show many colors (in the case of Iolite, violet-blue, light blue, and yellow-gray). Iolite is not rare and has a hardness of 7 - 7.5. Iolite is found in Sri Lanka, India, Madagascar and Burma. IPB IPB is an abbreviation for Ionized Plated Black. IPG IPG is an abbreviation for Ionized Plated Gold. IRIDESCENT An iridescent object displays many lustrous, changing colors. Iridescence is caused by the reflection of light from the jewel. IRIDIUM Iridium is a metal related to platinum. Iridium and platinum are frequently alloyed together, since the iridium increases the workability of the platinum. Iridium is also used for the points of gold-nibbed pens. IRRADIATED DIAMONDS Irradiated diamonds are diamonds that have been exposed to radiation. This changes the diamond's color (as the radiation changes the crystalline structure of the diamond). The change in the diamond is permanent. Older radiation treatments involving exposing the stone to radium; newer treatments bombard the stone with atomic particles in a cyclotron (which accelerates protons, neutrons, or alpha-partices to high speeds). The irradiated stones take on a greenish or an aquamarine hue. Irradiations of diamonds was first done in 1904 by Sir William Crookes, who exposed diamonds to radium, giving them a permanent greenish color; his diamonds are still slightly radioactive (at the level of radium-painted watch). Newer irradiation techniques bombard the crystal with atomic particles in a cyclotron, and then the stone is heated to about 800 degrees Centigrade, producing a stone with very little radioactivity and a permanent color change. IRRADIATION Irradiation is the act of being exposed to radiation. Many stones (like kunzite) are irradiated in order to enhance their color. Being irradiated changes the crystal structure of the mineral by moving electrons. Irradiation techniques bombard the crystal with high-energy radiation (like gamma rays), producing a stone with very little radioactivity and a change of color. Some color changes caused by Irradiation are permanent, others care unstable and be reversed by heating or exposure to sunlight. For example, colorless topaz changes to a cinnamon brown color after ibeing irradiated with cobalt-60 radiation, but the color fades as the stone is exposed to sunlight. A new method of irradiation changes clear topaz to a brilliant, non-fading blue. ITALIAN LAPIS Italian lapis is not lapis; it is actually blue-dyed jasper from Italy. IVORY Ivory is elephant tusks (the large, upper incisor teeth), which used to be carved into beautiful jewelry, trinkets, and piano keys. The finest ivory is the white African elephant ivory; Asian elephant ivory is yellower. Ivory has a complex characteristic grain which helps distinguish it from imitations. Using ivory is now banned since elephants are in danger of going extinct. Other tusk-like material is often substituted for ivory, including walrus tusks, whale teeth, hippopotamus teeth, animal bone, palm seed, and more recently, plastics. Vegetable ivory comes from the inner seed of the South American ivory palm and was used for small items, like dice. Synthetic ivory is made from plastics (like celluloid) and is called "French Ivory," Ivoride, Ivorine, or "Genuine French Ivory."
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