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Hyderabad hydrostatic weighing method PDF Print E-mail
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Friday, 21 September 2007

Hyderabad. A state in India; also the name of its capital city. The modern name for Golconda, the ancient source of some of the world's finest and most famous Diamonds. The old fortress of Golconda is situated seven miles northwest of the present city.

See GOLCONDA, INDIA.

hydro-cyclone separation. A gravel concentrating process which uses the hydro-cyclone, a very efficient ma­chine employing the same princi­ple as the heavy media separator. Gravel and broken blue ground are fed in from the side and a centrifuge motion is effected as the heavier frac­tion moves to the outside and down the conical-shaped tank. The lighter fraction flows to the middle and is forced upwards and floated off; and the heavier fraction sinks to the bot­tom and is extracted, as seen in the diagram.

hydrostatic weighing method. The determination of the specific gravity of a gemstone or other substance by weighing it immersed in water and also in air. The S.G. is then stated as the ratio between the weight in air, and the loss of weight in water (i.e., the difference between the air and water weights). The general formula for specific gravity is:

weight in air

weight in air - weight in water

. See

diamond BALANCE, SPECIFIC GRAVITY, SPECIFIC-GRAVITY ATTACHMENTS.

Last Updated ( Thursday, 01 November 2007 )
 
Horatio diamond into the possession of the Shah of Persia Hortensia Diamond PDF Print E-mail
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Friday, 21 September 2007

Horatio diamond. A misnomer for rock crystal from Arkansas.

Hornby Diamond. Thought to have been brought to England from the East Indies by the Honorable William Hornby, Governor of Bombay, in 1775. It was reported by Streeter in 1882 to weigh about 36 carats. One writer of the nineteenth century ex­pressed the belief that it later came


into the possession of the Shah of Persia (Iran). Ownership has been denied by the Central Bank of Iran in Tehran, where the Crown Jewels are kept. However, Dr. V. B. Meen re­ported in 1966 that a 38.18-carat trapezoid-shaped diamond among the Crown Jewels of Iran could be the Hornby.

Hortensia Diamond. A lovely and unique peach-colored stone of 20 carats that was doubtless worn by Hortense de Beauharnais, Queen of Holland (1783-1837), who was the daughter of Empress Josephine, wife of Louis Bonaparte and mother of Napoleon III. The catalog of the Apollon Gallery, Louvre Museum, Paris, states that the stone was pur­chased by Louis XIV and that la­ter, after the robbery of the Royal Treasury in 1792, it was retrieved from its hiding place under a roof in Les Halles district. It is now on ex­hibition in the Louvre.

Hot-Springs diamond. A misnomer for rock crystal.

Howeson Diamond. A 24-carat sap­phire blue diamond reported in 1953


to be in the possession of the widow of the late John Howeson of London. There is no later report of it.

 
Hope Diamond PDF Print E-mail
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Friday, 21 September 2007

Hope diamond. The 45.52-carat, dark-blue Indian stone known as the Cutting history of the Hope Di'. Hope is undoubtedly one of the world's most celebrated Diamonds, although far from being the largest. The origin of the Hope Diamond has been highly speculative until re­cently. A study by H. Tillander (1975) of the dimension and weight figures from the stages of the cutting of the Tavernier Blue resulting in the Hope Diamond indicate that: (1) The Tavernier Blue had been recut three times to the present gem, the Hope; and (2) no other stones may possibly have resulted from any of the recut-ting operations. (See diagram of evolution of the Hope Diamond.) Past investigators believed that a similarity of color between the Hope and the 13.75-carat Brunswick Blue Diamond suggested that the two stones were the result of recutting the 69.03-carat French Blue Diamond. The French Blue, which was stolen from the Garde Meuble (French Royal Treasury) in 1792 and never recovered, was a "heart-shaped" stone. The Hope first appeared on the scene at the London market in 1830 and was purchased for the gem collection of Henry Philip Hope for $90,000. After Hope's death in 1839, the stone became the possession of

his nephew, Henry Thomas Hope, who displayed it at the 1851 Crystal Palace Exposition. By this time, it had acquired its official name. When the wife of Henry Thomas Hope died in 1887, she bequeathed the now-famous diamond to her youthful grandson, who was her daughter's son and the Duke of Newcastle, if he would agree to adopt the official name of Hope: Henry Francis Hope Pelham-Clinton Hope. This he did, reasoning that the great value of the diamond would more than compen­sate for the cumbersome name! In 1894, Lord Hope married Mary Yohe, the American actress. After the mar­riage, she had a glass model made of the big blue stone for a stage come­back, which proved unsuccessful. Later, in 1906, it was said that Lord Hope was in dire financial straits and that he sold the gem in part payment for his debts. In 1908, Abdul Hamid II, Sultan of Turkey, is reported to have paid $400,000 for it. Later he was threatened by revolution and returned it to Paris to be resold. Then, in 1911, Pierre Cartier acquired the Hope in Paris and sold it for $154,000 to Edward B. McLean, then owner of the Washington Post

(Washington, D.C.), as a gift for his wife. Mrs. McLean's wealth came from the fabulously rich Camp Bird Mine near Ouray, Colorado. Despite the legends surrounding the Hope, including about a dozen violent deaths and disasters to two royal houses, she never considered the stone unlucky, even though her life was plagued by a number of per­sonal misfortunes. Following Mrs. McLean's death in 1947, Harry Winston, New York City gem mer­chant, purchased the famous stone for $179,920 and presented it to the Smithsonian Institution in Wash­ington, D.C., where it is on perma­nent exhibit. In 1962, it was one of the features of the Ten Centu­ries of French jewelry exhibition at the Louvre Museum, Paris, France. Note: At the suggestion of Dr. Her­bert Tillander, a recent reweighing (1975) of the Hope Diamond by Robert Limon, C.G., showed it weighed in at exactly 45.52 carats instead of the 44.50 carats as previ­ously reported in the literature. Hopetown. A town in Cape Pro­vince, Republic of South africa, and the location of minor alluvial dia­mond diggings. Current production is inconsequential. It was the lo­cation of the discovery of South Afri­ca's first diamond (1886).

Last Updated ( Thursday, 01 November 2007 )
 
high shoulders Holland Diamond Holland Syndicate Homansvlei Hope Diamond PDF Print E-mail
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Friday, 21 September 2007

high shoulders. A pear shape cut in such a way that the heel end of the


stone has a flattened appearance with square-shaped corners rather than a true semi-circular outline. This is usually done in order to retain more weight. See belly, head, heel,pear shape.

H.L.G.,

Ltd. A mining company that operates alluvial-diamond deposits in the Lichtenburg and Barkly West districts, Republic of South africa. It is a wholly owned subsidiary of De Beers Consolidated Mines, Ltd.

Hoffman, M. K. A German scientist who, in 1931, repeated the experi­ments of Moissan in an effort to pro­duce synthetic Diamonds, but with­out success. See moissan, Ferdinand

FREDERIC HENRI; SYNTHETIC DIAMOND.

Holland Diamond. A 36-carat conical-shaped diamond reported in the 19th century to be in the Crown Jewels of the Netherlands. It has never been authenticated. Present whereabouts unknown. Possibly, this is the Bantam Diamond seen in Java by Tavernier. See bantam diamond.


Holland Syndicate. A Dutch dia­mond-mining company that works al­luvial deposits in Ghana (Gold Coast), Africa. Annual production is approx­imately 200,000 to 250,000 carats. See

GHANA.

holohedral class (ho'-low-he"-dral).

See hexoctahedral class.

Holpan. A minor alluvial diamond deposit in the Barkly West area, Cape Province, Republic of South Af­rica. Production from these diggings amounted to less than 200 carats in one recent year.

Homansvlei. A minor alluvial dia­mond deposit in the Schweizer Reneke area, Transvaal Province, Re­public of South Africa. The yield from this digging in one recent year was less than 100 carats. Hondsriever. A minor alluvial dia­mond deposit in the Bronkhorst-spruit area, Transvaal Province, Repub­lic of South Africa.

Hope Diamond. The 45.52-carat, dark-blue Indian stone known as the

 
Hebron Herbert Herkimer diamond hexagon cut hexoctahedron Higgshope PDF Print E-mail
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Friday, 21 September 2007

Hebron. A minor alluvial diamond deposit in the Barkly West area, Cape Province, Republic of South Af­rica. The total output in one recent year was less than 1400 carats.

heel. The rounded end of a pear-shaped stone opposite the point. See

PEAR SHAPE, BELLY.

Herbert. A town in Cape Province, Republic of South africa, and the lo­cation of minor alluvial diamond diggings.

Herkimer diamond. A misnomer for rock crystal from Herkimer Co., New York.

Hershey, Dr. J. W. An American in­vestigator who carried out research into the problem of diamond syn­thesis at McPherson College, Kansas, in 1938. By using a variation of the molten-iron process of Crookes and Moissan, he claimed to have pro­duced synthetic Diamonds, but there is no proof that his experiments were successful. In 1940, he wrote The Book of Diamonds, in which his method is discussed. See crookes, sir


WILLIAM; MOISSAN, FERDINAND FREDERIC HENRI; SYNTHETIC DIAMOND.


hexagon cut. A hexagonal (i.e., six-sided) form of cutting, usually step cut with all sides of equal length. hexoctahedral class (hex-ahk'-tah-he"-dral). A name given to the high­est symmetry class of the cubic, or isometric, crystal system. Diamond is in this class. Synonymous terms are holohedral class and normal class

(hex-ahk'-tah-he"-dron). One of the seven basic forms in the highest symmetry (hexocta­hedral) class of the cubic, or iso­metric, crystal system. It has 48 trian­gular faces, with each plane face in­tersecting all three crystallographic axes. Although there are a number of hexoctahedrons that differ in respect to the inclination of their faces, this form can be visualized as an oc­tahedron, with each of the faces hav­ing been replaced by six triangular faces. See cubic system, hexoctahedral

CLASS, OCTAHEDRON.

hextetrahedron. An isometric crystal form of tetrahedral symmetry having 24 similar faces with unequal inter­cepts of all three axes. See cubic sys­tem.

Higgshope. A minor alluvial dia­mond deposit in the Hopetown area,

 
heat treatment (of diamond) heavy liquid heavy-media separation PDF Print E-mail
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Friday, 21 September 2007

heat treatment (of diamond). Heat­ing a diamond or other material at a given temperature for a specified period to permit a partial or com­plete readjustment of the atomic structure that was previously altered by some type of treatment. For example, an irradiated diamond that has turned green may be changed to other colors by heat treatment. See

CYCLOTRON-TREATED DIAMOND, PILE-TREATED DIAMOND.

heavy liquid. A high-density liquid that is used to determine the specific gravity of Gemstones. Gems float if their specific gravity is lower than the density of the liquid, remain sus­pended if it is the same as that of the liquid, or sink if it is higher than that of the liquid. The S.G. of diamond is 3.52. The most commonly used


liquids for testing gems are methy­lene iodide (S.G., 3.32), pare bromo-form (S.G. 2.89), diluted bromoform (S.G. 2.85) and bromoform diluted with xylene to a density of 2.62. A transparent liquid with a density of 3.52 may be made by diluting C/er/c/'s solution slightly with distilled water. See specific gravity.

heavy-media separation. A recovery method for Diamonds, based on the principle that an agitated suspension of finely ground solids in water be­haves as a heavy liquid. A suspen­sion with an effective specific gravity of 2.95 and the characteristics of a true heavy liquid is obtained by agi­tating the proper mixture of finely ground ferrosilicon and water. When crushed blue ground is fed into this


liquid, the diamonds and other dense materials settle to the bottom and the lighter materials remain suspended or rise to the top. By using this method, over 80% of the worthless material is separated from the dia­monds and other heavy particles. See

HEAVY LIQUID, SPECIFIC GRAVITY.

 
Hawaiian diamond head magnifier stone graders heart-shaped brilliant cut PDF Print E-mail
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Friday, 21 September 2007

Hawaiian diamond. A misnomer for rock crystal.

head. A term sometimes used for heel, the rounded end of a pear-shaped stone opposite the end ter­minating in a point. See heel, pear shape.

head magnifier. A simple binocular magnifier that is worn on the head by jewelry repairmen and manufac­turers and by diamond and colored-

stone graders. Many diamond grad­ers believe that their efficiency in color grading is increased slightly by low magnification.

Heart Diamond. Tavernier, the French jeweler and traveler, saw this 35-carat heart-shaped brilliant mounted in an ornament in the trea­sure of Aurangzeb of India. Addi­tional details lacking.

. A heart-shaped variation of the brilliant cut that is related to the pear shape. The round end is flattened and indented and the girdle diameter across the shoulders is widened until the


diameter is approximately equal to the length.


heat conduction. Diamond has a very high thermal conductivity, the highest of any known material which is why they initially feel cold to the touch. Extremely heat-conductive Type I la stones are used as heat sinks to conduct heat away from materials or delicate instruments. heat, effect on diamond. Transparent diamond will burn in oxygen at about 800°C, with carbon dioxide as the product. In air (approximately 20% oxygen) the temperature of com­bustion is about 875°C, although a figure as low as 690°C. has been reported. Diamond will convert to graphite by heating it in a vacuum to between 1200°C. and 1900°C. At approximately 3700°C, in a non-oxidizing atmosphere under control­led conditions, theoretically the diamond would melt. The heat from a jeweler's torch may cause the sur­face of a diamond to become leaden and cloudy, but the condition can be corrected by repolishing. In exces­sive heat, greater than 800°C, the color may be removed from treated Diamonds. Excessive heat may also cause an undesirable color change in an irradiated diamond; e.g., a green cyclotron-treated stone. Rapid tem­perature changes may cause the de

velopment of internal imperfections or an increase in the number or size of cleavages or fractures already pres­ent, due to the unequal expansion of included minerals. A flawless diamond, however, suffers very little change of volume with change of temperature. Therefore, although care should be taken, sudden tem­perature changes are much less likely to cause cracks in diamond than in many colored stones. See

THERMAL EXPANSION (OF DIAMOND).

Last Updated ( Friday, 21 September 2007 )
 
Hartebeestlaagte Hastings Diamond Hatton Garden Haute-Guinea PDF Print E-mail
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Friday, 21 September 2007

Harlequin diamond. An important part of the Wurttemberg Crown Jew­els, the 22-carat Harlequin Diamond was originally set in a Golden Fleece for Duke Karl Alexander (1733-1773). It is now set as a pendant in a three-row, 97-stonediamond necklace and is on display in the Wurttem­berg Landsmuseum, Stuttgart, Ger­many.

Harry Young Diamond. A 269.50-carat light yellow diamond octahed­ron discovered in 1913 on the Vaal River, Cape Province, Republic of South africa. Ultimate disposition unknown.


Hartebeestlaagte. A minor alluvial diamond deposit in the Ventersdorp area, Transvaal Province, Republic of South Africa. A production of less than 200 carats was reported for one 12-month period in the late 1950's.

Harvard Diamond. A near-perfect, 82-carat yellow octahedron was once part of the James A. Garland collection, Peabody Museum, Har­vard University, Cambridge, Mas­sachusetts. It was stolen in 1962 and never recovered.

Hastings Diamond. A political scan­dal ensued when this 101-carat diamond was presented to King George III in 1786 by Warren Hast­ings, Governor General of India, as a gift from the Nizam of the Deccan. Hastings, already under a cloud (la­ter impeached) for his inept ad­ministration of India, was accused of trying to bribe the King with the diamond. Further historical details lacking.

Hatton Garden. The center of the London diamond and wholesale jewelry district.

Haute-Guinea. Upper Guinea, the most important diamond-producing area in Guinea (formerly French West Africa). See guinea.

Haute-Sangha. The most important diamond-mining district in the Cen­tral African Republic. The principal company operating here is Compag-


nie Miniere de I'Oubangui Oriental (CMOO).

 
Gunsons Sortex Limited Guyana PDF Print E-mail
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Friday, 21 September 2007

Gunsons Sortex Limited. London manufacturer of machines for sorting seeds who developed an X-ray diamond sorting unit that was install­ed in several De Beers treatment plants. Concentrates are passed under an X-ray beam and when any diamond fluoresces, a photomulti-plier tube causes an air jet to deflect the stone into a diamond catch bin.

See X-RAY SEPARATOR.

Guyana. Formerly British Guiana in South America. The first discovery of Diamonds on the north coast of South America occurred in Guyana in 1890 in the gravels of the Maza-runi River, which is the largest pro­ducing region today. Of less impor­tance are the gravels of the Cuyuni, Puruni, Potaro and Berbice Rivers. Annual production is less than 50,000 carats, with about 60% of the total yield being industrial grade. Mining is done mostly by individuals or by two- or three-man crews using crude equipment. Diamond produc­tion in 1975 was reported to be 13,000 carats industrial and 8,000 carats gem quality. gypsy (gipsy) setting. Mounting in which the stone is deeply set into the metal so that the table facet is almost level with the metal surface. A popu­lar setting with diamonds in the 19th century; also, used with poor quality diamonds or diamond simulants.

 
grupiaras Guinea Guise Diamond PDF Print E-mail
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Friday, 21 September 2007

grupiaras. A Brazilian term for dia­mond-bearing valley deposits.

Guenther, P. L. A German scientist who, in collaboration with two as­sociates, R Gessele and W. Reben-tisch, attempted to produce synthetic Diamonds in 1942 by utilizing spe­cial apparatus that permitted pres­sure up to 120,000 kilograms per square centimeter and temperatures as high as 3500°C. Numerous tests with multiple variations were carried out. The duration of the experiments varied as well as the method of quick cooling. In addition to pure melted iron, mixtures of iron with man­ganese, silicon, beryllium, lithium and nickel were used in conjunction with both coal and graphite. Of the few minute particles that were pro­duced, none was proven to be diamond. Guenther considered his experiments a failure. See synthetic

DIAMOND.

Guinea. Formerly French Guinea, a country in French West africa. A major producer of alluvial diamonds, particularly in Upper Guinea (Haute-Guinea), to the east of Sierra Leone and north of Liberia. Recorded exports have been much smaller than production, because much of the output has been smuggled into Liberia. Estimated diamond produc­tion for 1975 was 55,000 carats in­dustrial and 25,000 carats gem qual­ity. See FRENCH WEST AFRICA, KEROUANE.

Guise Diamond. A 28.44-carat rose-colored diamond reportedly purchased by Louis XIV in 1665 from his cousin, Marie of Lorraine. Previ­ously it had belonged to Henry, Duke of Guise, for whom it was named. The 1691 inventory of the French Jewels listed the Cuise at 33


carats. Later, by 1774, it had been recut into a rectangular shape weigh­ing 28.39 carats. Subsequently, it was stolen from the Garde Meuble in the great French jewel robbery of 1792. It was recovered and in the 1811 inventory it weighed 28.72 carats. The Guise was sold in 1888 and its weight listed as 28.44 carats. There is no later report of it and its whereabouts is unknown.

 
Griqualand West Griqualand West Diamond-Mining Co PDF Print E-mail
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Friday, 21 September 2007

Griqualand West. An alluvial diamond-mining area in the Repub­lic of South africa; a division of Cape Province. The historic mining town of Kimberley is situated in this area.

Griqualand West Diamond-Mining Co. A diamond-mining company in the Republic of South Africa, control­led by De Beers Consolidated Mines, Ltd. This company owns the Du-toitspan Mine, comprising 512 claims, at Griqualand West, Cape Province.

grizzly. A screen used for sorting blueground at the diamond mines. 5-, 2- and iy4-inch screens are used.

Grodzinski, Paul. Until his death in 1957, one of the outstanding au­thorities in the industrial applications of diamond and other hard materials. He was head of the Industrial Diamond Information Bureau, editor and cofounder of the Industrial Diamond Review, and editor-in-chief of the Bibliography of Industrial Diamond Applications. For many years he was a member of the Educa­tional Advisory Board of the Gemological Institute of America. In addition to his many papers and arti­cles, he wrote Diamond Tools (New York, 1944) and Diamond Technol­ogy (London, 1953).

Grootdoorns. A minor alluvial dia­mond deposit in the Bloemhof area, Transvaal Province, Republic of South Africa. Annual production is negligible.

Grootlaagte. A minor alluvial dia­mond deposit in the Schweizer Ren-eke area, Transvaal Province, Repub­lic of South Africa. The annual yield from this mine is very low.


Grootpoort. A minor alluvial dia­mond deposit in the Schweizer Ren-eke area, Transvaal Province, Repub­lic of South Africa. The yearly yield from this mine is very low.

growth line. Lines which affect light in a manner that makes them visible as a banded effect within the stone, as well as on the surface. Under cer­tain lighting conditions, this banded effect usually is revealed parallel to octahedral faces, so that four sets of growth lines may be observed. Growth lines are hard to detect. See

POLYSYNTHETIC TWINNING, TWINNING LINES, KNOT LINE.

growth markings. The surfaces of crystals often have markings that are characteristic of the material. Diamonds show characteristic fea­tures for different crystal forms. Oc-tahedra usually show triangular de­pressions, called trigons, oriented in reverse to the orientation of the face on which they appear. Dodecahedra are usually grooved parallel to the long direction of each face, and cubes have square or rectangular depressions at 45° angles to the edges of the face. See trigon.

 
Great Star of Africa Diamond PDF Print E-mail
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Friday, 21 September 2007

Great Star of africa diamond. See

CULLINAN (I) DIAMOND.

Great Table Diamond. A legendary stone, supposedly seen by Tavernier in the 17th century. It reportedly weighed 242 French carats, or 250 metric carats and its shape was flat and oblong, with one corner broken off. Also called White Tavernier Diamond and Table Diamond.


Great White Diamond. See victoria

DIAMOND.

Green Brilliant Diamond. A 40-

carat, green, brilliant-cut diamond, described by a writer in 1882 as hav­ing been worn by the King of Saxony (1697-1733) as a button in the plume of his hat. It should not be confused with the Dresden Green Diamond, a 41-carat pear-shaped stone. The Green Brilliant was on display in the Green Vaults of the Dresden Histori­cal Museum prior to being confis­cated by the Russians in 1945. It was subsequently returned to the Mu­seum in 1958.

green diamond. A naturally green, yellowish-green, apple-green or olive-green diamond of a sufficiently pronounced color to be an asset. Such a stone is called a fancy. Fine green stones are extremely rare. Some have been described as emerald green, but it is doubtful if this color exists. The 41-carat Dres­den Green Diamond has been de­scribed as an emerald-green stone, but it is actually yellowish green. A stone turned green by emanations from radium, a cyclotron or a ra­dioactive pile should not be called a green diamond without being pre­ceded by a descriptive term or terms to show the origin of the coloration. Many green Diamonds of a lighter tint are mined, particularly in Sierra Leone.

Green Dresden Diamond. See Dres­den GREEN DIAMOND.

Grima

Diamond. A 55.91-carat pear-shaped diamond, reportedly of "fine white" color and "internally flawless," was purchased in No­vember, 1972 by Andrew Grima at the Christie's sale in Geneva.

 
Greater Namaqualand Great Mogul Diamond PDF Print E-mail
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Friday, 21 September 2007

Greater Namaqualand. See namaqua-

LAND.

Great Harry diamond. A large (exact size unrecorded) lozenge-shaped diamond that was part of the Scottish Crown Jewels that James VI took with him when he became James I of England. At the time (about 1605), he had it mounted with other gems in a jewel known as the Mirror of Great Britain. There is no trace of this diamond today.

Great Mogul Diamond. Found in India in the middle of the seven­teenth century, the Great Mogul is said to have weighed 787.50 carats in the rough. It was among the trea­sures of the famous Shah Jehan, builder of the Taj Mahal and owner of the Koh-i-Noor. He ruled a power­ful empire just north of Golconda, in India, where Diamonds were first discovered. Aurangzeb, the son of Shah Jehan, showed the great gem to the French traveler and gem expert, Tavernier, presumably the only Euro­pean to see it. Tavernier, who said it resembled "the half of an egg cut through the middle," published a picture of it, from which all known


replicas have been made. The Great Mogul was a rose-cut stone and weighed only 280 carats, according to Tavernier's reckoning, at the time he saw it. He was told that Hortensio Borgio, a Venetian who cut the stone from the original 787.50-carat rough, did such a poor job that the Mogul refused to pay him; rather, he fined him 10,000 rupees, his entire for­tune. The further history of the stone is unknown, but it is believed to have been among the loot carried off by the Persians after the sack of Delhi in 1739. Curiously, the descrip­tion of the Orloff closely resembles that of the Great Mogul, except in weight, and some experts think that it is the same stone and that Taver­nier may have miscalculated in trans­lating the Indian rati, or diamond weight (1.87 grams), into the Euro­pean standard, the carat.

 
Greater Bear Diamond PDF Print E-mail
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Friday, 21 September 2007

Greater Bear diamond. A 114.37-carat rough diamond found in the Mir Pipe. Now in the U.S.S.R. Dia­mond Fund in Moscow.

Great Beginning Diamond. A 135.12-carat rough diamond discov­ered in the Mir pipe. Now in the U.S.S.R. Diamond Fund in Moscow.

Great Blue Diamond. See wittelsbach

DIAMOND.

Great Brazilian Diamond. This 130-carat diamond was once part of the Crown Jewels of Portugal. In 1956, it was claimed to have been set in a $1,250,000 diamond necklace and exhibited at Sears Roebuck stores. Its present owner and location are un­known.

Great Chrysanthemum Diamond. In the summer of 1963, one of the most unique and exciting events in many years occurred in the South African diamond fields: The discovery of a beautiful 198.28-carat, fancy-brown diamond. This unusual stone was purchased by Julius Cohen, New

York City manufacturing jeweler, under whose direction it was fashioned by the cutting firm of S & M Kaufman into a 104.15-carat pear-shape. It has a total of 189 facets (67 on the crown, 65 on the girdle, and 57 on the pavilion) and measures 25 millimeters wide, 39 long, and 16 2/10 deep. In the rough state, the diamond appeared to be a light, honey color; after cutting, however, it proved to be a deep, rich golden brown, with overtones of sienna and burnt orange, the warm colors of the brown chrysanthemum; hence, the name. It is mounted as the central stone in an extraordinary yellow-gold necklace of 410 oval and marquise-shaped Diamonds, the value of which is stated by the owner to be $540,000. The Great Chrysan­themum has been exhibited by sev­eral leading retail jewelers in the United States and was shown as a Diamonds International Awards win­ner in 1965. In the same year, it was displayed at the Rand Easter Festival in Johannesburg, Republic of South africa.



Last Updated ( Friday, 21 September 2007 )
 
Grao Mogol Grasfontein Graspan PDF Print E-mail
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Friday, 21 September 2007

Grao Mogol. A former diamond producing region in Minas Gerais, Brazil. This district was soon worked out, but in 1839 approximately 2000 garimpeiro were engaged in mining. graphite. A polymorph (allotrope) of elemental carbon. It occurs in tabu­lar crystals of hexagonal outline with a prominent basal plane usually in foliated or scaly masses. Graphite's structure consists of carbon atoms forming flat hexagonal sheets of six-membered rings with-loose bonds between sheets (3.25 A units apart whereas in diamond the closer 1.42 A units is far stronger), consequently graphite is very soft. Cleavage is parallel {0001}, hardness 1-2, black color, black streak, metallic luster, greasy feel, specific gravity 2.09-2.23, melting point about 3,500°C, an electrical conductor. Usually found in metamorphic rocks. See

DIAMOND, LONSDALEITE.

Grasfontein. One of the more impor­tant alluvial diamond deposits in the Lichtenburg area, Transvaal Province, Republic of South africa. Production


for a recent year was about 3800 carats. In 1927, it was the scene of one of the greatest rushes in dia­mond-mining history; it was also one of the most orderly and spectacular.

Graspan. A minor alluvial diamond deposit in the Schweizer Reneke area, Transvaal Province, Republic of South Africa. The yearly yield from this mine is very low.

grease belt. An endless, grease-coated belt that utilized the same principle as the grease table for the recovery of Diamonds. Grease belts have largely superseded grease ta­bles. See GREASE TABLE.

grease table. A device for separat­ing diamonds from other heavy min­erals after concentration of crushed blueground. Since water does not adhere to the surface of a clean diamond, diamonds adhere to the grease. Other minerals are wetted and are washed over the slanted rocking tables. See kirsten, f. b.

greasy luster. See luster.

 
grain grain line Grand Conde Diamond PDF Print E-mail
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Friday, 21 September 2007

grain. (1) One-quarter of a metric carat (0.0500 grams or 0.25 ct.), a unit of weight commonly used for pearls and sometimes for other gems. (2) Cleavage, sawing or polishing di­rections in diamond. When used alone, the word grain usually refers to the cleavage direction, but may refer to sawing and polishing direc­tion. See CLEAVAGE (IN DIAMOND), CUBE, DODECAHEDRON, POLISHING, SAWING.

grainer. Stones with weights near multiples of 0.25 ct., or one grain, are referred to as grainers, qualified by the appropriate numerical desig­nation; e.g., four-grainer for a one-carat stone.

grain line. See twinning line.

Grand Conde Diamond. See le

GRANDE CONDE DIAMOND.

Grand Duke of Tuscany Diamond.

See FLORENTINE DIAMOND.

Gran Sabana. One of the important diamond fields in Venezuela. See

VENEZUELA.

grao. A Brazilian weight for dia-


monds and other gems; the equiva­lent of about Vi carat.

 
Goniometer Good Hope Gordon Diamond PDF Print E-mail
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Friday, 21 September 2007

Goniometer. An instrument used to measure the angles between crystal faces.

Goniometer contour print. A photo­graph of light points reflected from the crown facets of a faceted stone (diamond). See identigem.

Good Hope. A minor alluvial dia­mond deposit in the Barkly West area, Cape Province, Republic of South africa. Annual production from the diggings here is negligible.

Good Hope Diamond. See star of Per­sia DIAMOND.

goods. Mining companies, marketers of rough, cutters, importers and wholesalers, often refer to categories of their diamond merchandise as goods. See close goods, common goods,

GRADED GOODS, LOOSE GOODS, MOUNTED GOODS, OUTSIDE GOODS, POLISHED GOODS, SAWED GOODS, WHOLE GOODS.

Gordon Diamond. A slightly yellow 30-carat rough diamond crystal was reportedly discovered by a Belfast land surveyor between 1862 and 1866 in South Africa. Among other geological specimens that he brought back to Ireland in 1866 was a piece of fibrous quartz in which was em­bedded a crude diamond. A Belfast jeweler noticed the diamond and sent it to Antwerp for evaluation. Its history after cutting is unknown. Like the Platberg and Charlemont Dia­monds, this diamond's discovery pre­cedes that of the Eureka Diamond.

Gordon Orr Diamond. A 62-carat rough diamond of exceptional qual-


ity that was found in the Wajrah Karur Mines, Bellary District, India, in 1883. It was cut into a 24.85-carat brilliant. The present location of this stone is not known.

gorgulho. A Brazilian term for frag-mental diamond-bearing material as­sociated with clay in plateau de­posits. See cascalho.

Gornyak Diamond. The Gornyak rough reportedly weighs 44 carats and is valued at 100,000 rubles. It was found in Yakutiya, Siberia and presently is in the Russian Diamond Fund, Moscow. Governador Valladares Diamond.

See BENEDITO VALLADARES Diamonds I, II, AND III.

Government Diamond Office (Sierra Leone). A Sierra Leone government diamond buying, selling, and market­ing organization managed by Dl-CORWAF. GDO was established in 1959.

Goyaz Diamond. A Brazilian dia­mond that was found on the Ver-issimo River, State of Goyaz, in 1906. Existing records, which are vague and incomplete, indicate that the rough weighed 600 carats and that one of its cleavage fragments was fashioned into an 80-carat stone. No additional information is available.

graded goods. Diamonds that have been graded by the cutter, importer or wholesaler before sale to the re­tailer, in contrast to melange offering. See goods, melange.

Graduate Gemologist. One who holds the Graduate in Cemology Diploma, awarded by the Gemologi-cal Institute of America, after suc­cessful completion of either its cor­respondence or full resident courses

 
Golconda d'Or Diamond PDF Print E-mail
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Friday, 21 September 2007

Golconda d'Or diamond. Consid­ered to be the largest emerald-cut golden diamond in the world, this historical stone was recut by Asscher of Amsterdam from its original 130 carats and now weighs 95.40 carats. The Golconda d'Or is notable be­cause it is one of the last large Diamonds taken from the old Gol­conda Mines of India. First men­tioned in 1739 as part of the booty taken from Delhi by the Persian in­vader Nadir Shah, it reportedly was later handed down to the Sultan of Turkey in the early 19th century. In 1909, the first President of the Turkish Republic, Mustafa Kemal Ataturk, sold the Golconda d'Or to a wealthy Turkish family. It was later purchased by Dunklings, the Jewelers, Mel-


bourne, Australia, in 1962, where it is now on permanent display.

Gold Coast. See ghana.

Golden Dawn Diamond. Found in 1913 on the Vaal River, Cape Pro­vince, Republic of South africa. 133 carats. Cut to a 61.50 brilliant. Auc­tioned in 1926 to the Aga Khan for $24,000, in whose family it presum­ably remains today. Golden Maharaja. A fine quality of golden color pear-shaped diamond, weighing 65.60 carats. The Golden Maharaja attracted international at­tention at the 1937 World's Fair in Paris for its beauty and, especially, the unusual color.

Golden Pelican Diamond. Aptly named for the Pelikaanstraat, An­twerp's famous diamond center, where it was cut and polished, the 64-carat, golden, emerald-cut Co/d­en Pelican has been exhibited in Canada and Switzerland and in 1958 at the Diamond Pavilion at the Brus­sels World's Fair by its owners, E. Severy and M. Ginsburg of Antwerp. It was valued by the owners at $50,000.

Gong Gong. One of the early diamond diggings on the Vaal River,


Cape Province, Republic of South Af­rica. Now an insignificant producer, the Gong Gong diggings produced only approximately 600 carats in one recent year.

 
glazier's diamond Godavari River Goedvooruitzicht Golconda Diamond PDF Print E-mail
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Friday, 21 September 2007

glazier's diamond. Bort or small fragments of diamond crystals for cutting glass.

glets (or glatts, glatze, gletz). A word of Dutch origin for a feather in a diamond. It is a cleavage crack that looks like a feather. See feather.

gletsen. Plural of glets.

Goa. A city in India through which the Portuguese imported Brazilian Diamonds in the early part of the 18th century to suggest Indian origin. After the discovery of diamonds in Brazil in 1725, they were difficult to sell. The European and Indian mer­chants feared that the sudden influx of Brazilian stones on the market would cause prices to drop, so they claimed that the stones were "too hard to cut" or that they were actu­ally inferior Indian diamonds that had been shipped to Brazil to fool buyers. Probably a number of other yarns were concocted. The Brazilian dealers neatly offset this difficulty by shipping the diamonds by way of the Indian port of Goa and selling them as Indian stones.

Godavari River. A river in Hyder­abad and Madras, India. At one time a source of diamonds.

Goedehoop. A minor alluvial diamond deposit in the Christiana area, Transvaal Province, Republic of South africa. The annual yield from this deposit is inconsequential.

Goedgedacht. A minor alluvial diamond deposit in the Ventersdorp area, Transvaal Province, Republic of South Africa. A production of less


than 200 carats was reported for one recent year.

Goedvooruitzicht. A minor alluvial diamond deposit in the Lichtenburg area, Transvaal Province, Republic of South Africa. Total production for one recent 12-month period was only 364 carats.

Goias. A minor diamond-producing state in Brazil. See brazil.

Goias Diamond. A 600-carat rough discovered early in 1906 along the Verissimo River, Goias, Brazil. Re­ported to have been discovered by an old man who was neither knowl­edgeable as a prospector nor in gem testing procedures. The diamond was later shattered by a blow from a hammer since diamonds were gen­erally believed by some to be inde­structible. Later, two fragments were identified as diamond. It is believed that the original crystal size was comparable to a box of matches or weighed possibly in excess of 600 carats. The original crystal was de­scribed as very deformed. From the two remaining fragments only one stone of approximately 8 carats was cut.

Golconda. (1) The name of a city in India that was the center of the diamond trade in the 17th century. (2) A name used to refer to the an­cient alluvial-diamond deposits to the south and east of the city of Gol­conda along the Pennar, Kistna and Karnul Rivers; also referred to as the Kistna Croup. See Hyderabad, india. (3) A color grade that is seldom used to­day. It refers to a highly transparent (limpid) stone, either entirely without body color or with a faint bluish cast.

Golconda Diamond. A 30-carat emerald cut diamond of fine color and clarity which was for many years

in the "Collection of Registered His­toric Gems" of Trabert & Hoeffer, Inc., New York City jewelers. Their description calls it "one of the last large diamonds from the old Indian Mines." It was purchased by R. J. Reynolds, tobacco millionaire, in 1960, for $70,000 and given to Muriel Greenough, who became the third Mrs. Reynolds.

Last Updated ( Friday, 21 September 2007 )
 
girdling glass PDF Print E-mail
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Friday, 21 September 2007

girdling (also called rounding up, bruting or cutting). The step in the fashioning process of a diamond in which the stone is given its circular shape. The stone is held in a lathe, or cutting machine, and another dia-mond, called a sharp or tool stone, which is affixed to the end of a long dop that is supported by the hands and under an armpit, is brought to bear against the stone being shaped. An older method con­sisted merely of rubbing two Diamonds together until the desired shape was obtained. glanzloserdiamant. German, mean­ing a cloudy diamond; a dull sur­face; without luster.

glass. An amorphous substance pro­duced by the fusion of oxides at high temperatures that can be manufac­tured to have a range of physical properties. There are two principal types of glass, the crown glasses, made of silica, potash, soda, and lime; and the flint glasses with lead oxide replacing the lime of the crown glass. The flint or "lead" glass, especially when thallium com­pounds are added, is the most impor­tant. Because of its high dispersion and brilliance, lead glass is a com­mon substitute for diamond and other Gemstones. See paste. mines for well-shaped, clear transpa­rent diamond crystals of good color with bright faces and without visible inclusions. (2) A term sometimes used to refer to a fashioned diamond that lacks brilliancy.

Last Updated ( Friday, 21 September 2007 )
 
girdle area PDF Print E-mail
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Wednesday, 19 September 2007

girdle area. See girdle

girdle facet. Small, plane or approx­imately plane, polished surfaces which are placed upon the girdle.

girdle (or break) facets. The 32

triangular facets that adjoin the girdle of a round brilliant-cut stone, 16 above and 16 below. Also called upper- and lower-break facets, upper- and lower-girdle facets, top-and bottom-half facets, skew facets, skill facets, or cross facets. Facets are also sometimes placed directly on the girdle, in which case the stone is usually said to have a faceted girdle.

See BRILLIANT CUT (ROUND), POLISHED GIRDLE.

girdle plane. A plane passing through the girdle of a stone separat­ing the crown from the pavilion.

girdle reflection. Reflection of the girdle as seen in the internal surface of the pavilion facets when viewed through the table.

girdle thickness. The width of the out­er edge, or periphery, of a fashioned diamond or other gemstone. In a rounded style of cutting such as the round brilliant, pear shape or marquise, the girdle edges, when viewed parallel to the girdle plane, consist of undulating lines caused by the intersection of the flat fac­ets with the curved girdle. In such stones, the girdle thickness is mea­sured across the midpoints of oppos­ing upper- and lower-girdle facets. In well cut stones, this dimension is suf­ficient to prevent this narrower por­tion of the girdle from being knife edged, but it does not exceed 1 % of the girdle diameter in stones of ap­proximately 0.50 to 2.0 carats. In smaller stones, the relative thickness is greater; in larger stones, smaller. Essentially, the girdle should appear

 
Ghana Diamond Corp PDF Print E-mail
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Wednesday, 19 September 2007

Ghana diamond Corp. One of the

companies in Accra, Ghana, that is licensed by the government of that country to buy Diamonds from native miners. See ghana.

GIA (Gemological Institute of America) Color-Grading System. A color-grading system for colorless to yellow diamonds that utilizes the let­ters D through Z for a colorless-to-yellow scale. These grades are set in relation to a series of master dia­monds thatare maintained in the


GIA's Los Angeles Laboratory. This range of the alphabet was purposely chosen to avoid confusion with the numerous trade systems employing letters starting at the beginning of the alphabet. See chart in Appendix enti­tled, Comparison of Several Different Diamond Color Grading Systems. See also color grade, master (or keyi

diamonds.

GIA Color Grader. An accessory in­strument designed and manufactured by the Gemological Institute of America to facilitate the color grad­ing of diamonds under binocular magnification and to demonstrate it readily to customers.

GIA Diamond Grader. A gemologi­cal microscope designed and man­ufactured by the Gemological Insti­tute of America. It consists of a binocular microscope mounted on an illuminator base and is equipped with a mechanical stoneholder, iris-diaphragm light control, light-and-dark-field illumination, tiltback, and a turntable. Accessories for propor­tion and color grading extend its use.

GIA Jewelers' Camera. Predecessor of the Photostand. See photostand. girdle. The outer edge, or periphery, of a fashioned stone; the portion that is usually grasped by the setting or mounting; the dividing line between the crown and pavilion. On step-cut diamonds, on almost all fancy bril­liant cuts, and on some round brilliant-cut diamonds the girdle is polished. On brilliant-cut styles, the polished girdle may or may not be faceted. An unpolished girdle surface should be so smooth that it has a waxy luster. See bearded (or fuzzy) gir­dle, BRILLIANT CUT (ROUND), GIRDLE THICKNESS, KNIFE-EDGED GIRDLE, LUMPY GIRDLE, POLISHED GIRDLE, GIRDLE PLANE, WAVY GIRDLE.

 
General Electric Co PDF Print E-mail
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Wednesday, 19 September 2007

General Electric Co. See borazon,

SYNTHETIC diamond.

geology. The science of the earth concerned with the systematic study of the rocks and minerals, in which are preserved a record of changes produced by agents and processes that have long been active on the earth's surface and deep within it. Also includes the study of ancient life.

German diamond. A misnomer for

rock crystal.

German South-West africa. See

SOUTH-WEST AFRICA.

Gessele, P. See cuenther, r l.

GGG. See gadolinium gallium garnet.

Ghana (formerly Gold Coast). An

important alluvial diamond-pro­ducing country in Africa. The first discovery was made in 1919. The principal deposits are in the Birim River Valley, about 65 miles north­west of Accra, and along the Bonsa River. The stones are small and of rather poor quality. Overall produc­tion is on the order of 85% indus­trials and 15% gem quality. The mines are operated principally by Consoli­dated African Selection Trust (CAST); smaller concerns are Cayco, Ltd., Akim Concessions, Ltd., and the Hol­land Syndicate. Independent native miners, who account for the bulk of


the total production, are organized into the African Diamond Diggers' Association, which has a predomi­nantly Nigerian membership, and the African Diamond Winners' Associa­tion, which is composed entirely of Ghanese. Annual production from both mining companies and inde­pendent diggers is usually in excess of 3,000,000 carats. All Diamonds now won in Ghana are required by law to be sold on the Accra Dia­mond Market.

 
gem Gem Instrument Corporation PDF Print E-mail
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Wednesday, 19 September 2007

gem. (1) A cut-and-polished stone that possesses the necessary beauty and durability for use in jewelry; also, a fine pearl. (2) A term often applied to an especially fine speci­men; e.g. a gem diamond. In this use, the meaning depends on the ethics and the range of qualities handled by the seller. (3) As an ad­jective, a prefix; e.g. gem quality, gem crystal, etc. (4) As a verb, to decorate with gems. (5) A rough diamond that has the necessary shape, purity and color to enable it to be cut for jewelry purposes. Only about 20% of all Diamonds can be thus classified.

gem color. When employed ethi­cally, this term is approximately synonymous with perfection color. However, it is often used in lieu of a definite grade to imply that a diamond of average to good color is actually exceptional in color. See per­fection COLOR.

Gemette. Trade name for synthetic sapphire.

gem gravel. Alluvial deposits


(gravels) in which gems are found.

See ALLUVIAL DEPOSITS, ALLUVIAL SORTING, RIVER DIGGINGS, WET DIGGINGS.

Geminair. Trade name for man-made yttrium aluminum garnet (YAG)..

Gem Instrument Corporation

(GEM). On January 1, 1977, the In­strument Division of the Gemologi-cal Institute of America became a separate, wholly-owned subsidiary named Gem Instrument Corporation. The new corporation is under the same management, with Richard T. Liddicoat, Jr., President; Gale M. Johnson, Vice President, Manufactur­ing; and Kenneth M. Moore, Vice President, Sales. GIA laboratory and instructor gemologists will continue to have the opportunity to use and to make suggestions for new instru­ments before designs are finalized; thus, the unique system of designing and testing by people who have to use the instruments is retained.

Gemolite (trademark, Gemological Institute of America). A diamond


and gem illuminator-magnifier com­bination. It utilizes wide-field bi­nocular stereoscopic zoom mag­nification, an advance form of mag­nification that permits a continuous change of magnification between the upper and lower limits of the mi­croscope, with a base designed for the examination of diamonds and col­ored stones by either dark-field or light-field illumination. The base contains a diffuser, an adjustable baf­fle, a diaphragm to adjust to various lighting needs, and a turntable to permit the instrument to be turned around to the customer. Three Gemolite models with different zoom magnification ranges are a-vailable: Deluxe Mark V; Custom Mark V Model A; and Custom Mark V Model 8. Also called Cemscope.

See DARK-FIELD ILLUMINATION, LIGHT-FIELD IL­LUMINATION, MICROSCOPE.

 
Garde-Meuble PDF Print E-mail
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Wednesday, 19 September 2007

Garde-Meuble. The French Royal Treasury. Noted for the great gem robbery of September 17, 1792 in which the French Blue diamond and other notable Diamonds were stolen and some never recovered. Now call­ed the Ministere de la Marine. See

FRENCH BLUE DIAMOND.

garimpeiro. A Brazilian term for an unlicensed diamond miner or pros­pector.

garniture de diamants. French, meaning set with diamonds.

Garry Moore Diamond. Niels Bach of Ludington, Michigan, discovered this stone in 1960 at the "Crater of

Diamonds State Park" near Mur-freesboro, Arkansas. He named it in honor of the well-known radio and television personality Garry Moore, who had visited the mine after hav­ing Howard Miller, owner of the diamond-bearing property, as a guest on his television program. The diamond is a yellow modified trisoc-tahedron weighing 6.43 carats; it is flawless and only slightly etched. Schenck & Van Haelen, New York City diamond cutters, appraised it at $6,000.

GDO. See government diamond office

(SIERRA LEONE).

 
Gaby Delys Diamond gadolinium gallium garnet gamma ray PDF Print E-mail
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Wednesday, 19 September 2007

gabon. A minor diamond-producing country on the west coast of Central africa.

Gaby Delys Diamond. Given by an unknown Indian maharajah to the late, famous actress, Gaby Delys, for whom it is named. A 28.25-carat, yellow, heart-shaped stone. Later owned by dancer Florence Walton and the "Mystery Chef" of American radio fame. Present owner unknown.

gadolinium gallium garnet. Man-made gem material manufactured by the Czochralski process. Often called GGG or 3G. Is chemically an alumi-nate and not a silicate and therefore not a true garnet since it contains no silica even though it has the garnet structure. The stones are singly re­fractive, cubic, have a specific grav­ity of 7.05, dispersion of 0.038, and a refractive index of 2.03. The hard­ness is 6%. Used as a diamond sim­ulant.

Galliant. Trade name for man-made "gadolinium gallium garnet" (GGG).

gamma ray. High frequency, ex­tremely short wave length elec­tromagnetic radiation emitted from the nucleus of an atom during radioactive decay. Most stones treated by gamma irradiation acquire a bluish-green color of shallow penetration which can be polished off. Some Type lib Diamonds are photoconductive to gamma rays and can be used like a geiger tube as a counter for gamma irradiation.

Ganspan. A minor alluvial diamond deposit in the Schweizer Reneke


area, Transvaal Province, Republic of South Africa. This digging makes a negligible contribution to total South African production
 
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