Whether it’s understanding gemological or jewelry terms in an article you’re reading or simply gaining a greater understanding of the world of jewelry and gemstones, our Jewelry & Gem Dictionary is a handy reference guide. And, unlike most dictionaries, ours makes for interesting reading all on its own!
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 (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 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.
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.
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 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.
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.
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 (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 stands for the Gemological Institute of America, recognized as a top authority on grading gemstones.
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.
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.”
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.
The girdle is the narrow band around the widest perimeter of a gemstone. The setting in a piece of jewelry usually grasps the stone around the girdle.
Givre beads are beads made of transparent glass fused around a translucent core. Givre means frost in French.
Glass is often used in jewelry, as beads (faceted or spherical), rhinestones and as poured glass.
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 is the art of engraving gemstones, making intaglio and cameos. Stones are engraved using grindstones with powdered emery or diamond as an abrasive
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 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 (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 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.
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 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.
Gemstones are frequently sent to an independent laboratory such as the GIA, AGS, NGL, or AGTA to be graded against a master set of gemstones, according to an industry-wide common set of grading guidelines. These grades are compiled to form a complete appraisal which offers an assessment of the worth of a gemstone.
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.
A grain is a unit of weight used for diamonds and natural pearls. Four grains are equal to one carat.
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 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 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 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 is gold that has been alloyed with a higher percentage of silver than copper.
Green rouge is chromium dioxide, which is used to polish precious metals, giving them a luster.
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.
Grelots are small beads that have an elongated, pendant shape.
Grey gold is gold that has been alloyed with 15-20% iron.
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 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 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 is a metal alloy that is composed of 90 percent copper and 10 percent tin.
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.
A gypsy ring (also spelled gipsy) is a ring with a recessed stone or stones. Also known as “star setting.”