Jewelry Dictionary (G)

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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.

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:

- Grossular - Colorless, orange, yellow, pink, or brown
- Pyrope - Colorless, pink, or red
- Pyrope Almadine - Red-orange to red-purple
- Almandine spessartine - Red-orange
- Chrome pyrope - Orange-red
- Almandine - Orange-red to purple-red
- Hessonite - Yellow-orange to red
- Spessartine - Yellow-orange
- Topazolite - Yellow to orange-yellow
- Malaia - Yellow to red-orange to brown
- Andradite - Yellow-green to orange-yellow to black
- Demantoid - Green to yellow green andradite
- Tsavorite - Green to yellow-green
- Pyrope-Spessartine - Green-yellow to purple
- Color-change garnet - Blue green in sunlight; purple-red in incandescent light
- Transvaal "jade" - Bright green grossular garnet
- Uvarovite - Emerald green
- Grape - purple
- Rhodolite - Purple-red
- Xalostocite - Pink grossular 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:

- Yellow Gold - 50% silver and 50% copper
- White Gold - Nickel, zinc, copper, tin and manganese
- Pink (rose) Gold - 90% copper and 10% silver
- Green Gold - High proportion of silver or cadmium
- Blue Gold - Some iron
- Grey Gold - 15-20% iron

Karat - Percent Gold :

- 24 Kt. - 100% Gold
- 18 Kt. - 75% Gold
- 14 Kt. - 58.3% Gold
- 10 Kt. - 41.7% Gold

GOLD DORE

Gold dor? (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-plaqu? 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."