|Progress Diamond proportion of diamonds to blue ground proportions ProportionScope Punch Jones Diam|
|Written by Administrator|
|Sunday, 23 September 2007|
proper proportions (of a diamond).
See AMERICAN CUT; TOLKOWSKY, MARCEL; PROPORTIONS; PROPORTIONS, GOOD.
proportions. A term that meant originally the distribution of the mass of a fashioned diamond above and below the girdle. Use by diamond men has broadened its meaning to include the major factors that determine cutting quality; i.e., total depth as a percentage of the girdle diameter, table diameter, girdle thickness, facet angles, symmetry, and even details of finish. See proportions, good;
CUTTING; AMERICAN CUT; TOLKOWSKY, MARCEL; FINISH; SYMMETRY.
ProportionScope. A diamond-grading instrument designed and first manufactured by the Gemological Institute of America in 1967. It is an optical comparator for the checking of the proportions of a brilliant. It combines lenses and movable mirrors to project the silhouette of a diamond on a screen. Line diagrams of Tolkowsky proportions on the screen, as well as a "zoom" range, enable
proportions, good. The proportions derived mathematically for the optimum treatment of light are seldom cut today. Present tastes among jewelers apparently have been conditioned somewhat by the weight saving and cost reduction made possible through "spreading," for slightly larger tables and thinner crowns. However, there is general agreement that the angles of the Tolkowsky Theoretical Brilliant Cut are optimum, so any stone of good proportions should have a 403/4° pavilion angle, 34 Vi" crown (bezel), (and a girdle of medium thickness). See
AMERICAN CUT, SPREAD STONE, SWINDLED STONE, PROPORTIONS.
Province of the Cape of Good Hope (also called Cape Province or the Cape). A province in the Republic of South Africa, the north-east and east-central portions of which have been, and are, important diamond-producing areas. The famous mining town of Kimberley is in Cape Province near the boundary of the Orange Free State.
puinwassers. A term used to describe washers of old tailing (waste washers) in the South African diamond fields. pulsator jig. See jig.
Punch Jones diamond. One of the largest United States Diamonds, this 34.46-carat greenish-gray crystal was found in 1928 on Rich Creek near Peterstown, West Virginia. It was discovered by Grover C. Jones and his son, William R "Punch" Jones, while playing horseshoes but was not positively identified as a diamond until 1943, when it was examined and tested by Professor Roy J. Holden of Virginia Polytechnic Institute. It is now on permanent display in the Smithsonian Institution, Washington, D.C.
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