Colored Stones 4 Key Terms PDF

Colored Stones 4 Key Terms Absorption spectrum—A pattern of dark vertical lines or bands shown by certain gems when viewed through a spectroscope. Interference—Interaction between two light rays with the same wavelengths as they travel along the same path. Adularescence—The cloudy bluish white light...

Colored Stones 4 Key Terms Absorption spectrum—A pattern of dark vertical lines or bands shown by certain gems when viewed through a spectroscope. Interference—Interaction between two light rays with the same wavelengths as they travel along the same path. Adularescence—The cloudy bluish white light in a moonstone, caused by scattering of light. Intervalence charge transfer—A process where two transition elements with different valences exchange electrons to selectively absorb light. Allochromatic—A gem colored by trace elements in its crystal structure. Iridescence—A rainbow effect created when light is broken up into spectral hues by thin layers. Asterism—Crossing of chatoyant bands, creating a star in the dome of a cabochon. Aventurescence—A glittery effect caused by light reflecting from small, flat inclusions within a gemstone. Charge transfer—The movement of electrons back and forth between ions, causing the selective absorption of light. Chatoyancy—Bands of light in certain gems, caused by reflection of light from many parallel, needle-like inclusions or hollow tubes. Irradiation—Exposing a gem to manmade radiation to change or improve its color. Labradorescence—A broad flash of color in labradorite feldspar that disappears when the gem is moved. Milk and honey—A two-toned effect seen when a chatoyant gem is positioned at right angles to a light source. Optic axis—Direction of single refraction in a doubly refractive gem. Orient—Iridescence seen in some natural and cultured pearls and mother-of-pearl. Color center—A small defect in the crystal structure of a material that can absorb light and give rise to a color. Phosphorescence—Continued emission of visible light after UV or X-ray stimulation stops. Color change—A distinct change in gem color under different types of lighting. Play-of-color—The flashing rainbow colors in opal, produced by the interaction of visible light with the gem’s microscopic internal structure of stacked silica spheres. Diffraction—A special kind of interference phenomenon that produces patches of pure spectral colors. Dispersion—The separation of white light into spectral colors. Pleochroism—When a gem shows different bodycolors from different crystal directions. Refraction—Change in speed and possible change in direction of light as it travels from one material to another. Double refraction—When a gem’s crystal structure splits light into two rays that each travel at a slightly different speed and direction. Selective absorption—Process by which a material absorbs some components of visible light and transmits others. Doubling—The appearance of double images of a gemstone’s facet junctions on the side opposite the viewer. Single refraction—When a gem’s crystal structure doesn’t change incoming light other than by refraction and absorption. Fluorescence—Emission of visible light by a material when it’s stimulated by ultraviolet or X-ray radiation. Transition elements—Elements that can selectively absorb some wavelengths of visible light and produce color in gems. Idiochromatic—A gem colored by an element that is an essential part of its chemical composition. Wavelength—The distance between two adjacent high points of an energy wave. 190