RICHARD WISE GEM COLLECTION
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| flawless Describing a gemstone with no visible inclusions under 10X magnification. flour Tiny inclusions that cause a “sleepy” effect in the key color of a gemstone. fluorescence A glow or color visible under ultraviolet light. fortification The technical term for stripes of color in chalcedony. “four Cs” The four factors used to analyze and discuss the beauty of a gemstone: color, clarity, cut, and crystal. Altered by author. Traditionally, color, cut, clarity and carat (weight) gamut limit The point on the tonal (light to dark) scale at which a given hue produces the most vivid saturation. girdle The outer edge of a faceted stone, the area of greatest diameter, usually the part where the prongs are placed when the gem is set. “holding the carat” A cutting strategy designed to produce a finished gem above a certain whole carat weight. hue The descriptive technical term for color; e.g., red, pinkish orange, and chartreuse are hues. ideal cut A specific set of proportions discovered by Marcel Tolkowsky in 1919 thought to produce the greatest brilliance and maximum dispersion in a round brilliant cut diamond. imperial Archaic term used to describe certain hues of topaz. incandescent Light produced by a flame, candle, campfire, or light bulb. inclusion Anything visible to the naked eye or under magnification in a gemstone, such as a foreign body or crack. A stone with an inclusion is described as included. See also eye clean, loupe clean intaglio Designs cut in a gemstone that appear in relief when the stone is pressed into a soft substance like clay. Opposite of cutting en cameo. iridescence The exhibition of prismatic (rainbow) colors on the surface of a gem. See also orient, overtone. kelvin A unit used to measure
light temperature. loupe clean Describing a flawless
gem; no visible inclusions under 10X magnification. mask A modifying color, usually brown or gray, that diminishes the saturation (brightness or vividness) of a gem’s hue. |
master stone Stone of a known color and quality used for comparing other gems of the same species or variety; also a diamond of known color grade used to determine the grade of other diamonds. modifier A color that changes the appearance (hue) of another, e.g., a primary hue such as red can be modified by a secondary hue such as orange, yielding an orangy red hue. Saturation modifer, see mask. Mohs scale A relative scale of gem hardness; talc is 1, diamond is 10. mosaic The complex visual scene in the face-up gem. See also multicolor effect. multicolor effect The display of divergent colors or tonal variations of the same color on a gem viewed in the face-up position. nacre The mother-of-pearl secretions of the mollusk; pearl essence. nailhead Dark center in a gem; see fish-eye. native cut A poorly proportioned gemstone supposedly fashioned by primitive means; considered pejorative. nightstone A term adapted by the author to describe a gem species or variety that looks its best in incandescent light, showing its most saturated hue. Traditionally, an opal that retains a strong play-of-color in low light environments. nonchromatic Without color; a colorless stone, without chroma; see also achromatic, achroic. off-color Insufficient color, or saturation, in a diamond to be considered good color. Used to describe colorless diamond with a strong tint of yellow. opaque Impenetrable by light; neither transparent nor translucent. Opacity is the quality of being opaque. orient The iridescent effect visible in finer quality pearls; also called overtone. overcolor A stone with a hue that is overly dark in tone, usually above eighty-five percent. overtone See orient. padparadscha Color of the lotus; a light to medium-toned pinkish orange to orangy pink sapphire. pair Two gems matching in color, cut, clarity, crystal, and diameter. parcel Gems sold as a group. pavilion The portion of a faceted stone beneath the girdle. |
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