31 Questions
What is the term for the pattern of dark vertical lines or bands shown by certain gems when viewed through a spectroscope?
Absorption spectrum
What is the process where two transition elements with different valences exchange electrons to selectively absorb light?
Intervalence charge transfer
What is the term for the cloudy bluish white light in a moonstone, caused by scattering of light?
Adularescence
What is the term for the crossing of chatoyant bands, creating a star in the dome of a cabochon?
Asterism
What is the term for the movement of electrons back and forth between ions, causing the selective absorption of light?
Charge transfer
What is the term for the glittery effect caused by light reflecting from small, flat inclusions within a gemstone?
Aventurescence
What is the term for the direction of single refraction in a doubly refractive gem?
Optic axis
What is the term for the two-toned effect seen when a chatoyant gem is positioned at right angles to a light source?
Milk and honey
What is the term for exposing a gem to man-made radiation to change or improve its color?
Irradiation
What is the term for the continued emission of visible light after UV or X-ray stimulation stops?
Phosphorescence
Which optical phenomenon occurs due to the interaction of visible light with a gem's microscopic internal structure?
Play-of-color
What is the term for the separation of white light into spectral colors?
Dispersion
What is the term for the change in speed and possible change in direction of light as it travels from one material to another?
Refraction
What is the term for the appearance of double images of a gemstone's facet junctions on the side opposite the viewer?
Doubling
What is the term for the distinct change in gem color under different types of lighting?
Color change
What is the term for a small defect in the crystal structure of a material that can absorb light and give rise to a color?
Color center
What is the term for the process by which a material absorbs some components of visible light and transmits others?
Selective absorption
What is the term for the emission of visible light by a material when it's stimulated by ultraviolet or X-ray radiation?
Fluorescence
What is the term for a gem colored by trace elements in its crystal structure ?
Allochromatic
What is the bands of light in certain gems, caused by reflections of light from many parallel needle-like inclusions or hollow tubes?
Chatoyance
When a gem crystal structure splits light into two rays that each travel at slightly different speed and direction it is called......?
Double Refraction
What is the term for a special kind of interference phenomenon that produces patches of pure spectral color?
Diffraction
What is the interaction between two light rays with the same wavelength as they travel along the same path ?
Interference
What is a gem colored by an element that is an essential part of its chemical composition?
Idiochromatic
What is an element that can selectively absorb some wavelengths of visible light and produce a color in a gem ?
Transition Elements
What is a rainbow effect created when light is broken up into spectral hues by thin layers?
Iridescences
A broad flash of color in labradorite feldspar that disappears when the gem is moved is called ...?
Labradorescence
The distance between two adjacent high points of an energy wave is called ...?
Wavelength
When a gem's crystal structure doesn't change incoming light other than by refraction and absorption is referred to as ....?
Single Refraction
What term describes a gem showing different bodycolors from different crystal directions ?
Pleochroism
What term describes a iridescence sheen in some natural and cultured pearls and mother-of-pearl ?
Orient
Study Notes
Optical Properties of Gems
- Absorption spectrum: a pattern of dark vertical lines or bands shown by certain gems when viewed through a spectroscope.
Light Interactions
- Interference: interaction between two light rays with the same wavelengths as they travel along the same path.
- Diffraction: a special kind of interference phenomenon that produces patches of pure spectral colors.
Phenomena in Gems
- Adularescence: the cloudy bluish-white light in a moonstone, caused by scattering of light.
- 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.
Color and 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.
- Charge transfer: the movement of electrons back and forth between ions, causing the selective absorption of light.
Optical Effects
- Chatoyancy: bands of light in certain gems, caused by reflection of light from many parallel, needle-like inclusions or hollow tubes.
- 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.
Gemstone Properties
- 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.
Luminescence
- Phosphorescence: continued emission of visible light after UV or X-ray stimulation stops.
- Fluorescence: emission of visible light by a material when it's stimulated by ultraviolet or X-ray radiation.
Other Phenomena
- 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.
- Dispersion: the separation of white light into spectral colors.
- Pleochroism: when a gem shows different body colors 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.
Test your knowledge of colored stones with this quiz on key terms, including absorption spectrum, interference, adularescence, and more! Learn about the properties and characteristics of different gemstones.
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