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A - Jewelry & Gem Dictionary
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AB stands for Aurora borealis (which means "northern lights"). Aurora borealis rhinestones have a special iridescent finish that shines with many colors. The iridescent surface is a result of a very thin layer of metallic atoms that have been deposited on the lower surface of the stone. This process was invented in 1955 by the Swarovski company together with Christian Dior.
Abalone is a mollusk whose shell is iridescent on the inside. Abalone is a source of mother of pearl, which is used in jewelry making.
The Accessocraft Products Corp. is a company that produces costume jewelry, belts, buttons, and other accessories in a variety of styles. Accessocraft was founded in 1935 in New York, NY, USA.
Acroite is a rare, colorless variety of tourmaline.
Acrylics are a type of thermoplastic, and include transparent and opaque in varied colors. Some commonly-known acrylics are lucite and plexiglas. The bangle above is made of confetti lucite.
Adamantine means having a luster like that of a diamond.
Adularia is a common type of moonstone, a whitish-bluish semi-translucent stone. Adularia is usually set as a cabochon. Adularia was very popular early in the 20th century and was extensively used in Art Nouveau jewelry. Adularia has a hardness of 6 and a specific gravity of 2.57.
Adventurine is a misspelling of aventurine (and sometimes known as goldstone) 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.
Agate is a variety of chalcedony (a family of microcrystalline quartz). Agate is a very common stone that is often used in jewelry. It is found in a wide range of colors, including black, gray, brown, reddish, green, pink, blue, and yellow. Agate can be flecked with color and is often banded, exhibiting layers of quartz. Agate is porous and takes dye easily; it is frequently dyed to enhance the coloration and the banding. White agate was used often in Victorian jewelry, mostly as a background. Moss agate has green, red or black dendritic inclusions. Onyx is agate whose bands are parallel. Eye agate has banding arranged in concentric circles. Agate has a hardness of 6.5 to 7 and a specific gravity of 2.6. The agate pin above is from Miracle.
African jade (also called Transvaal jade) is a misnomer for massive green grossular garnet that is mined in South Africa; it is not jade, but does look like jade. It can be light green, white, or pink
Alexandrite is a mineral (a type of chrysoberyl) that appears to be different colors depending on whether it is viewed in natural or artificial light. Alexandrite appears to be red when seen in candle light and blue to green when seen in fluorescent light. Alexandrite was discovered on the birthday of the Russian Czar Alexander II, and it was named in his honor. Alexandrite is mined in Russia, Brazil, Burma, Ceylon, and Rhodesia. Laboratory-produced alexandrite is common, and it is often sold as natural alexandrite. Alexandrite has a hardness of 8.5 and a specific gravity of 3.64-3.74.
The "Alexandrite Effect" is a phenomenon in which a stone appears to be different colors depending upon the type of light it is viewed in. For example, the stone alexandrite appears to be red when seen in candle light and blue to green when seen in fluorescent light. Many other stones exhibit the "Alexandrite Effect," including garnet and sapphire.
An alloy is a combination of two or more metals. Common alloys used in jewelry are: gold under 24 Kt (mixed with silver, copper, and/or other metals), sterling silver (92.5% silver, 7.5% copper), brass (roughly half copper, half zinc), bronze (at least 60% copper with tin and perhaps other metals), and pewter (tin, lead, antimony, and a bit of silver or copper).
Almandine is a type of violet-tinged variety of garnet that ranges in color from deep red to reddish-brown. Almandine is the most common kind of garnet. Star garnets are almandines that exhibit an asterism. Almandine has a hardness of 7.5 and a specific gravity of 3.85-4.20.
Alpaca (also spelled alpacca) is an alloy consisting of mostly copper (roughly 60 percent), and approximately 20 percent nickel, about 20 percent zinc, and about 5 percent tin. This metal is a silver substitute.
Amber is translucent fossilized tree resin (from conifers), a natural hydrocarbon that comes in many colors, including yellow, reddish, whitish, black, and blue. Amber is flammable. Rubbing amber produces static electricity. The word electricity comes from the Greek word for amber, "elektron." It used to be thought that amber possessed magical powers that protected the wearer from evil. Pressed amber consists of small pieces of amber that have been fused together to form a larger piece. Fake amber is easily made from plastics, and buyers must beware of cheap imitations sold as natural amber. Amber has a hardness of 2.5 and a specific gravity of 1.05-1.10.
An American ruby is actually a pyrope garnet (and not a ruby at all).
Amethyst (Greek for "not drunken") is a form of the mineral quartz, and is a relatively common gemstone. Amethyst is usually purple, but can range in color from pale lavender to a very deep, reddish purple to a milky color to green. Deeper-colored amethysts are more highly valued. The ancient Greeks believed that amethyst made one immune to the effects of alcohol. Synthetic amethysts are hard to distinguish from the real stone.
Ametrine is a variety of quartz, a mixture of amethyst and citrine. Ametrine is partially purple and partially orange-yellow.
Amorphous means without form. An amorphous gem, like jet, amber, or ivory, does not have a regular internal structure, like those gems that fall within the seven crystal systems.
An amulet is a protective charm that is worn. It is worn in the hope of protecting the wearer from evil or illness or to bring the wearer good luck.
Angelite (CaSO4); it is a pale blue variety of calicium sulfate = anhydrate (it is gypsum that has lost water and crystallized). The stone is quite brittle; crystals are transparent to transluscent. Angelite stone has a hardness of 3 to 3.5 (quite soft) and a specific gravity of 2.9 - 3.0.
Angelskin coral is a pale pink coral, from deep sea coral. Angelskin coral is one of the most valued colors of coral (red is also highly prized). Coral is an animal that grows in colonies in the ocean. Coral polyps secrete a strong calcium structure that is used in jewelry making. Coral ranges in color from pale pink (called angelskin coral) to orange to red to white. In jewelry making, coral is either carved into beads, cameos, or other forms, or is left in its natural branch-like form and just polished. It used to be thought that coral protected the wearer, so it was a traditional gift to children. Coral has a hardness of about 3.5 and a specific gravity of 2.6 to 2.7. Since it is composed of calcium carbonate, coral will effervesce if touched with acid. Imitation coral is made from glass, porcelain, or plastic.
Annealing is the process of heating a metal and then cooling it to make it more workable. As metal is worked (hammered, rolled, etc.), stresses make the metal brittle (the metal molecules are pulled into random structures during the working). Annealing the metal make the metal re-crystallize, putting the molecules in an orderly structure. The temperature (and amount of time it takes) for annealing a metal depends on what metal or alloy it is. Large pieces are annealed in an annealing oven; small pieces are annealed using a blow-torch.
Anodized metal has been through an electrochemical process which changes the molecular structure of the surface layer, giving it a thin, protective film. In the anodization process, the metal is placed in an acid bath (at the "anode" or positive end of the electrical circuit) and an electrical current is passed through the tank. This process causes a controlled oxidation of the metal's surface to occur (oxygen atoms bond to surface atoms of the metal). Aluminum is often anodized, as is magnesium, titanium, and tantalum. Anodized metal has a lustrous sheen; the anodizing process can produce colorful surfaces.
Apache tears (a type of obsidian) is a volcanic glass that is usually black, but is occasionally red, brown, gray, green (rare), dark with "snowflakes," or even clear. This glassy, lustrous form of obsidian is found in lava flows in the southwest USA. Obsidian is formed when viscous lava (from volcano's) cools rapidly. Most obsidian is 70 percent silica. Obsidian has a hardness of 5 and a specific gravity of 2.35. The pin above is mahogany (brown) obsidian.
Aquamarine is a transparent, light blue or sea-green stone that is porous. Today, blue aquamarines are more highly valued, but this was not true in the past, when sea-green stones were prized. Heat-treatment turns greenish stones bluer. The best aquamarines come from Brazil. Large aquamarines are relatively common. Aquamarines are usually faceted but when they are cabochon cut, a cat's eye effect or asterism may appear. Aquamarines belong to the beryl family of stones. Aquamarine has a hardness of 7.5-8 and a specific gravity of 2.65-2.85.
Aqua regia is a 3:1 mixture of hydrochloric acid and nitric acid. Aqua regia is used to test gold and platinum; it is just about one of the few substances that can dissolve gold and platinum.
Aragonite is a mineral that is rarely used for jewelry. It is transparent to translucent and can range in color from honey-colored to pale reds, blues and greens to clear or white. It forms hexagonal crystals, pyramidal crystals, chisel shaped crystals, and other shapes. Aragonite has a hardness of 3.5-4 (relatively soft) and a specific gravity of 2.9 g/cm3.(average). Its chemical composition is CaCO3 (it is a form of Calcium Carbonate). Aragonite is named for Aragon, Spain, where it was first found in 1790. Aragonite is also found in many other European, North African, and some North American locations.
An arcade setting (also called coronet or claw setting) is one in which the stone is held in by many metal claws around a metal ring.
Arctic opal is a blue-green stone that is a mixture of azuritea and malachite; it is not a type of opal at all. Arctic opal is mined in the Wrangle Mountains and the Chugach Mountains of Alaska, USA (near Anchorage).
Arkansas stone is an abrasive used in jewelry making. It is used to smooth metals.
Art Deco was a style popular from the mid-1910's until the mid-1920's. This style originated in Paris, France. Art Deco pieces are characterized by geometric lines and angles, with very few curves. This art movement eventually became bolder and evolved into Art Moderne.
Art Nouveau was a style popular from roughly 1895 until World War I. Art Nouveau pieces are characterized by curves and naturalistic designs, especially depicting long-haired, sensual women. Louis Comfort Tiffany made archetypal Art Nouveau pieces.
ARTS AND CRAFTS
Arts and Crafts was an artistic movement that produced hand-crafted pieces toward the end of the 1800's. Pieces purposely look hand-made, incorporating hammer marks and simple cabochon settings. The Arts and Crafts movement also revived the art of enamel.
An assay is a test of the purity of an alloy. A tiny piece of metal is scraped from the piece and the percentage of gold or silver is determined. Official assay offices determine whether a piece qualifies for an appropriate hallmark.
Joseph Asscher was an eminent diamond cutter who cut the 3,106 carat Cullinan diamond. Asscher worked in Amsterdam. In 1902, his company, the Asscher Diamond Co., developed and patented the Asscher cut, a squarish step cut with an almost octagonal outline. This new cut enhanced the fire and light of the stone; it had a small table, a high crown, wide step facets, a deep pavilion and square culet. This cut became very popular in Art Deco jewelry and was a forerunner of the emerald cut. Recently, the Royal Asscher Diamond Co. resumed production of the original Asscher cut diamonds.
An asterism is a star-like luminous effect that reflects light in some gemstones, like star.
An Australian ruby is actually a pyrope garnet (and not a ruby at all).
Aventurine feldspar is also called Sunstone (a variety of oligoclase). This gemstone varies from golden to orange to red-brown, and can be transparent or translucent. Sunstone is metallic-looking due to sparkling red, orange or green crystalline inclusions (these are hematite or goethite crystals). Sunstone is found in Canada, the USA (in Oregon, India, Norway, and Russia) This brittle stone has a hardness of 6 and a specific gravity of 2.63 - 2.67. Sunstone is not enhanced.
Aventurine quartz is a type of quartz that has sparkling flecks (inclusions) of mica or iron. These colors of this stone include red-brown, yellow, gray, and green. Aventurine quartz has a hardness of 7 and a specific gravity of 2.64-2.69. This stone is usually cut with a flat or rounded surface to maximize its sparkle. Aventurine quartz is found in India, Russia, and Tanzania.
The Japanese name for abalone pearls is Awabi pearls.
Axinite is an unusual, lustrous stone that is brown, yellow, blue, green or gray. Violet axinite is rare (and from Tasmania). It has both transparent and translucent varieties. Axinite is dichroic. Axinite has a hardness of 7 and a specific gravity of 3.3. Axinite is a boro-silicate of aluminum and calcium. It is used only as a mineral specimen and not in jewelry.
AXIS OF SYMMETRY
An axis of symmetry (also called a rotational axis) is an imaginary line around which an object can be rotated a certain number of degrees and look like the original shape. When two planes of symmetry intersect, they form a straight line, which is an axis of symmetry.
Azurite is a beautiful copper-based blue mineral that is often used in jewelry. The color ranges from very deep blue to pale blue. Azurite has also been used as a dye for paints and luxury fabrics. Azurite is hydrated copper carbonate; its chemical formula is Cu3 (CO3)2(OH) 2. Malachite (another copper-based mineral) and azurite are often found together. Azurite has a hardness of 3.5 to 4 (relatively soft) and a specific gravity of 3.7 to 3.9. Azurite is found in massive monoclinic crystals in Australia the southwestern USA, France, Mexico, Morocco, Namibia, Zaire, and Europe. Azurite is sometimes coated with a colorless wax or impregnated with plastic in order to enhance the color and increase the hardness.