Noor-ol-Ayn Diamond normal class North Star Diamond
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Friday, 21 September 2007

Noor-ol-Ayn diamond. See nur-ul-deen diamond.

Noor-un-Deen diamond. See nur

UD-DEEN diamond.

normal. In the study of light, the NORMAL is an imaginary line drawn perpendicular to the surface of an optically dense medium. The NOR­MAL may be drawn through any given point on any surface to de­scribe the behavior of light at that


point. See diagrams, ancle of refrac-

IION, CRITICAL ANCLE, CRITICAL ANCLE CONE, IOTAL REFLECTION.

normal class. See hexoctahedral class.

"north light." The traditional light source used in color grading dia­monds. North skylight or "north light" is illumination from the north­ern sky between 10 a.m. and 12 noon on a moderately overcast morning during the spring or fall. Custom has it that light reflected from the north sky affords the least variation of intensity and color, is relatively shadow free, and contains Ihe least amount of ultraviolet. How­ever, north skylight is not sufficiently c onstant from day to day, at different limes of the day, or from one locality to another to be entirely satisfactory as a light source standard. Also, be­cause of the presence of ultraviolet in sunlight, the color of stones that fluoresce blue improves in daylight. Consequently, GIA has developed a lighting system that closely approxi­mates the desirable qualities of north skylight for diamond color grading. The closest approximation for a true color balanced daylight, as used in Ihe GIA system, has a correlated color temperature of 6200° Kelvin. See diamondlux, diamondlite.

North Star diamond. A fancy 32.41-carat blue pear-shape cut from a 97-carat rough found in the Ja-gersfontein Mine. Baumgold Broth­ers bought, cut and polished the rough valued at $300,000 in 1969. No other information is available.

Nova Estrela do Sul (New Star of the South) diamond. A 140-carat


greenish diamond that was found in 1937 in the Abaete River, Minas Gerais, Brazil. The present location of this stone is unknown.