|lumpy Lunda lupren luster|
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|Friday, 21 September 2007|
lumpy (or thick) stone. A cut diamond that is unnecessarily deep, resulting in a loss of brilliancy. Stones are cut in this manner to gain additional weight from the rough, thus permitting them to be sold at lower per carat prices. Lumpy stones were common before the advent of the diamond saw, for much more weight could be retained from crystals of octahedral shape, if little were ground away from the crown and pavilion tips. See tolkowsky theoretical brilliant cut, too deep pavilion cut. (See photo.)
Lunda. An important diamond-bearing region in Angola. See angola.
lupe. The German equivalent of loupe.
lupren. Scandinavian diamond Nomenclature system (Scan. D.N.) term for internally flawless (IF).
luster. The appearance of a material's surface in reflected light, as determined by the quantity and quality of light reflected. Smoothness and re-
fractive index are the main factors affecting luster. The luster of most rough Diamonds is described as greasy; that of fashioned Diamonds as adamantine (from the Greek word adamas, meaning extraordinarily hard).
Lusterite. Trade name for synthetic rutile.
Lustigem. Trade name for man-made strontium titanate.
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