|Written by Administrator|
|Wednesday, 19 September 2007|
A variety of luminescence. The property of changing one kind of radiation to another; for example, the visible wavelengths emitted by a material when excited by invisible radiation such as X-rays, ultraviolet rays or cathode rays, as well as by certain other visible wavelengths. It is exhibited by ruby, kunzite, yellow-green synthetic spinel, some
Diamonds and opals, and many other substances. Diamond usually fluoresces blue, although occasional stones may glow light red, green, orange, yellow or subtle variations of these. If the fluorescence is sufficiently strong to alter the color of the stone when observed alternately under incandescent light and daylight, it is said to be fluorochromatic.
See LUMINESCENCE, PREMIER DIAMOND, PHOSPHORESCENCE, PHOTOLUMINESCENCE, ULTRAVIOLET, ULTRAVIOLET LAMP EMISSION SPECTRUM, FLUOROCHROMATIC, CATHODOLUMINES-CENCE.
fluoride coating. Coating used to temporarily improve the color of diamonds. Applied by vacuum sputtering to form coatings of only a fraction of wavelength in thickness. Sometimes recognized by iridescence of the surface.
fluorochromatic (floo'-row-kro'-mat"-ik). When fluorescence causes a diamond to change color when exposed alternately under two different kinds of visible radiation, such as incandescent light and daylight, it is said to be fluorochromatic; for example, a yellow stone that displays sufficiently strong blue fluorescence in daylight to make it appear bluish.
See FLUORESCENCE, PREMIER DIAMOND, TRANS-ICHROMATIC.
Fly Diamond. A 60-carat rough diamond reported to be a white octahedron was discovered in 1872 on the claim of Robert Spaulding and Antoine Williams at Waldeck's Plant, Vaal River, Cape Province, Republic of South africa. The Stewart or Spaulding Diamond was also discovered at this site by the same two prospectors. It is said that an inclu-
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