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MACHINE STAMPING Machine stamping (also known as die-stamping) is a process in which sheet metal is cut and shaped between two dies, forming a pattern in relief. Two steel dies are used, the male die has the design in cameo (protruding); the female die has the design hollowed out. The male die is put on top of the metal, the female die is put on the underside of the metal. The press is forcefully brought down onto the dies and metal, forcing the metal into the shape of the mold. Many medallions and mass-produced jewelry findings are made this way. MARQUISE Marquise cut stones have a shape like an oval with two pointed ends. MATINEE-LENGTH A matinee-length necklace is a single strand that is from 22 to 23 inches (56 to 58 cm) long. Matinee-length generally refers to a string of pearls that hangs to the top of the cleavage. MATTE FINISH A matte finish on a metal's surface is a soft, lustrous finish that reduces the metal's reflectivity. MELEE A melee is a small diamond, under .20 carat. MEMORY WIRE Memory wire is a tough, stiff wire that retains its shape. It is often used for necklaces and bracelets. MICROCRYSTALLINE Microcrystalline is a type of mineral structure in which the crystals are so small that they can only be seen using a microscope. vMICRON A micron is a unit of length equal to 0.001 mm (millimeter). MILK AND HONEY EFFECT The milk and honey effect is one in which the apparent coloring of a stone changes (from milky to the color of honey) as the angle of the light changes. When a light is shined on the stone, one side of the stone is the color of milk and the other is the color of honey. When the light changes direction, the color effect also shifts. Cat's-eye chrysoberyl can exhibit this milk and honey phenomenon. MILLEGRAIN A millegrain (or millegrain setting) is a setting in which the stone is secured by tiny beads [grains] of metal or a band of metal that is decorated with tiny beads of metal. MINE CUT Mine cut stones have a cushion-shaped girdle. This type of cut was popular in the late 1800's. MIXED CUT A mixed cut in one in which the style of the facets above and below the girdle are different. A standard mixed cut is brilliant cut above and step cut below. MOHS SCALE The Mohs Scale of Hardness measures a substance's hardness, that is, how resistant it is to being scratched. In the Mohs scale, which ranges from 1 to 10, one substance is harder than another if it can scratch it. For example, a diamond (hardness = 10) will scratch garnet (hardness = 6.5-7.5), but not the other way around, so a diamond is harder than garnet. This scale was invented by Austrian mineralogist Friedrich Mohs (1773-1839). MOLDED CAMEO Molded cameos are cameos that are made by the molding process and not by carving the material (as traditional cameos are). Molded cameos are usually made from plastic, glass, or porcelain that is formed in a mold. Often, two colors of material are used, one for the relief pattern (often depicting a person or scene) and another for the background. The molded cameo above is a Jasper ware porcelain cameo made by the Wedgewood Company. MONOCLINIC Monoclinic minerals have a crystalline structure in which there is one two-fold axis of symmetry. Jade, Malachite and moonstone are monoclinic. MOONSTONE Moonstone (orthoclase) is a semi-translucent stone that is made of albite and orthoclase feldspar. It is usually whitish-blue, but can be colorless, yellow, orange, gray, or even reddish. Moonstone is usually set as a cabochon. Moonstone was very popular early in the 20th century and was extensively used in Art Nouveau jewelry. Moonstone has a hardness of 6 and a specific gravity of 2.57. It is monoclinic; it has one two-fold axis of symmetry. Adularia is a common type of moonstone. Oligoclase is another type of moonstone; Labradorite and albite are rare forms. MOSS AGATE Moss agate (also called Mocha stone in Britain and the USA) is a green variety of agate. It is chalcedony that has dendritic (tree-like) inclusions of green (red or black) hornblende. The inclusions often form beautiful patterns. Moss agate has a hardness of 6.5-7 and a specific gravity of 2.6. Green moss agate is found in India, and some other locations. MOTHER-OF-PEARL Mother-of-pearl is the iridescent coating on the inside of oyster shells. Mother-of-pearl is used for jewelry, buttons, and other uses. |
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