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Halphen Diamond hand loupe Hannay, James Ballantyne PDF Print E-mail
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Friday, 21 September 2007

Halo Cut (trademark). See polished

GIRDLE.

Halphen diamond. Streeter gives the only known record of this diamond: "Almost the only specimen of Red Diamond is a gem of a carat weight, bought by the author and sold to the late Mr. George Samuel for £800." Alternate name Halphen Red Dia­mond. Halphen Red Diamond. See halphen

DIAMOND.

hand loupe. See loupe Hanger Diamond. A 123-carat pale yellow rough diamond found in the early days of the South African diamond rush. It was reportedly purchased by Capt. E. S. Hanger of the Bloemfontein Rangers about 1868. Hanger sent the stone to Amsterdam to be cut into a brilliant rose-cut gem. It was subsequently purchased by the Countess of Char-lemont from County Tyrone, Ireland in 1870 for £300 and deposited in a bank as a future investment. No other details are available. Hannay Diamonds. See hannay, james

BALLANTYNE.

Hannay, James Ballantyne (1855-1931). A Scottish chemist who, in 1880, claimed to have produced mi­nute diamonds by heating amor­phous carbon with bone oi I and metal­lic lithium under great pressure. At the time, there was no satisfactory method for proving or disproving Hannay's claims. Later efforts to du­plicate his experiments failed to pro-

Half-moon cut


duce diamonds. After World War II, a bottle labeled "Hannay's diamonds" was discovered in the British Museum of Natural History. Recent X-ray and cathodoluminescence tests have shown conclusively that the Hannay diamonds are all fragments of natural diamond. Since the Han­nay diamonds are barely visible to the naked eye, it is believed that some accidental contamination of the starting materials occurred. See

SYNTHETIC DIAMOND.

hardebank. A harder-than-usual type of kimberlite, or blue ground. See

BLUE GROUND, KIMBERLITE, YELLOW GROUND.

MOHS SCALE

Comparison of Mohs and the Knoop hard­ness scales.


hardness. The resistance of a sub­stance to being scratched. Diamond is 10 on Mohs scale of hardness. Tests prove that diamond is approxi­mately 10 to 150 times as hard as corundum, the next hardest mineral. The variation stems not only from differences obtained by different hardness-testing methods, but also from the fact that various directions on a given diamond's surface show a

 
habit hailstone bort hairline feather PDF Print E-mail
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Friday, 21 September 2007

habit. (1) The characteristic general shape of a crystal resulting from its internal structure and controlled by the environment in which the crystal grew. (2) The characteristic crystal form, including distinguishing ir­regularities, of a mineral. (3) Used to denote the general shapes of crystals; e.g., cubic, blocky, tabular, prismatic. Characteristic habits of diamond are usually octahedral, cubic, dodeca-hedral, and hexoctahedral, which may have somewhat rounded crystal faces and edges.

hailstone bort. A rounded type of bortthat differs greatly in appearance and structure from all other forms. Typically, it consists of alternating layers of gray to clear, poorly to well-crystallized minute diamond crystals. See bort.

hairline feather. See feather

half. A common abbreviation for a half carat.

half brilliant. Same as half-brilliant cut.

half-brilliant cut. A rarely used style of cutting that has a circular girdle outline, a flat, unfaceted base, and a standard brilliant-cut crown; i.e., 32 facets and a table. Also called half brilliant or brillionette. This cut isused principally to defraud, by set­ting in a gypsy-style mounting over foil arranged to simulate pavilion facets; thus, the stone appears much larger than it is.

 
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