National Diamond Mining . natural point negative crystal Nepal Diamond
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Friday, 21 September 2007

National diamond Mining Company (Sierra Leone) Ltd. See diminco. National Mineral Development Company (NMDC). A government agency in charge of exploration and development of mineral resources in India.

natural. A trade term for a portion of the original surface of a rough dia­mond that is sometimes left by the cutter on a fashioned stone, usually on the girdle. Naturals indicate an ef­fort to retain some extra weight from the original rough in the rounding-up and polishing operations. Some con­sider all naturals to be blemishes, whereas others contend that those that do not flatten the girdle outline nor extend beyond the width of a medium girdle should not be re­garded as blemishes. (See photo.)

natural grit. A term used to refer to diamond powder made by crushing natural Diamonds, as opposed to that consisting of man-made Diamonds,

called synthetic grit

. natural point. See point naif.

navet (nav-et"). A little-used English contraction of navette

. navette (nav-et"). From the French, meaning little boat. Navette and boat shaped are terms preferred in the colored-stone trade; marquise in the diamond trade. See marquise

Navsari. Indian diamond center.

Nawanger diamond. The 148-carat brilliant-cut Nawanger diamond was owned in 1970 by the Maharanee Gulabkumberba of Nawanger. It is reported to have come from Russia.

negative crystal. An angular cavity within a crystal or fashioned gem-stone, the outline of which coin­cides with a possible crystal form of the mineral in which it occurs. It is a rare occurrence in diamond.

Nepal diamond. Little is known about the beautiful 79.41-carat Nepal diamond, except that it is thought to have been mined in In­dia's Golconda region and that it was in the possession of Maharajah Bir Shumsher Jung Bahadur Rana of Nepal in the late nineteenth century. In 1901, it passed to his elder son,

Gehendra Shumsher, and it re­mained in the hands of Nepalese roy­alty until recent years. The stone has been described as striking and lovely in every respect colorless, flawless and well cut and polished. Mounted in an elaborate clip-brooch and pic­tured in the April, 1958 issue of Na­tional Geographic Magazine, it was then owned by Harry Winston, New York City gem dealer, who valued it at $500,000. It was shown at Lon­don's Ageless diamond Exhibition in 1959 and subsequently sold in 1961 to a private collector.