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commercially clean PDF Print E-mail
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Friday, 14 September 2007
"commercially clean." The com¬mon meaning of this misleading term is "reasonably free from inclusions." If a diamond were without flaws or blemishes, logically it would be called flawless or perfect. Sometimes highly flawed stones are represented as "commercially clean." The obvi¬ously misleading nature of the term has led the American Gem Society to prohibit its use by Society members. It is also prohibited by the Federal Trade Commission, unless the stone meets the Commission's definition of the term perfect. See FLAWLESS, PERFECT,
 
Comite' de Coordination de I'lndus-trie Diamantaire PDF Print E-mail
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Friday, 14 September 2007
Comite' de Coordination de I'lndus-trie Diamantaire. A Belgian organi¬zation, working in consultative con¬tact with the Government and the diamond Trading Co., Ltd., that is entrusted with the conciliation of in¬terests of the various sections of the diamond industry.
 
columns PDF Print E-mail
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Friday, 14 September 2007
columns. Huge rounded boulders (inclusions) embedded in kimberlite.
 
color, unevenness of PDF Print E-mail
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Friday, 14 September 2007
color, unevenness of. As in other Gemstones, the color of Diamonds is not always uniform. This is true in many crystals containing a very slight tinge of color. Color may be concentrated in spots or layers. In some octahedra, the points or ridges of the crystal contain color and the remainder is colorless. The reverse condition is true also. Although diamonds usually "lose color" when cut, merely because of the loss of bulk, the buyer of rough diamonds, because of the irregularities of color, cannot be sure of the precise color grades of the diamonds to be cut from tinted rough.
 
color print PDF Print E-mail
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Friday, 14 September 2007
color print. A complete color spec¬trum of a stone (diamond) recorded on graph paper by a recorder in conjunction with a Spectrophotome¬ter. Alternate spelling, colour print. See IDENTIGEM.
 
color of diamond PDF Print E-mail
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Friday, 14 September 2007
color (of diamond). (1) A general term that is used to designate this basic factor affecting a diamond's beauty and value. It includes all of the characteristics related to a diamond's color. See COATED DIAMOND; COLOR GRADE; COLOR (UNEVENNESS OF); CYCLOTRON-TREATED DIAMOND; DISPERSION; ELECTRON-BOMBARDED DIAMOND; FANCY DIAMOND; FLUORESCENCE; FLUOROCHROMATIC; HEAT TREATMENT (OF DIAMOND); PHOSPHORES¬CENCE; PILE-TREATED DIAMOND; RADIUM-TREATED DIAMOND; TRANSICHROMATIC. (2) Synonymous with color grade.
 
colorless PDF Print E-mail
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Friday, 14 September 2007
colorless. A transparent diamond or other gemstone completely devoid of body color. ~
 
colorimeter PDF Print E-mail
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Friday, 14 September 2007
colorimeter. An instrument for measuring color. The ACS electronic colorimeter incorporates a selenium cell that measures the relative trans¬mission of yellow and blue light by a diamond brilliant. Colorimeters are also manufactured and used in Europe. See ACS COLOR-GRADING SYSTEM, COLOR GRADE.
 
Color Grader PDF Print E-mail
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Friday, 14 September 2007
Color Grader. An accessory instru¬ment used to accurately establish the color grades of Diamonds under mag¬nification by comparing stones with a color graded (standardized) set of diamonds.
 
color grade PDF Print E-mail
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Friday, 14 September 2007
color grade. The relative position of a diamond's body color on a colorless-to-yellow scale. Since few gem Diamonds are other than color¬less to yellow, color grades are not used to classify other hues; instead, they are merely referred to as fancy diamonds (except light browns, which are treated approximately as comparable depths of yellow). A number of color-grading systems are used by various dealers to classify diamonds on the colorless-to-yellow scale. The range of color encompass¬ed by any specific term used in a given system rarely corresponds to that of terms used in other systems. Terms usually vary in meaning to dif¬ferent graders, unless they are related to color-grading systems based on definite comparison standards availa¬ble to all dealers and the public alike. See chart in Appendix. See ACS COLOR-GRADING SYSTEM, BODY COLOR, BROWN DIAMONDS, COLORIMETER, DIAMONDLITE, CIA COLOR GRADING SYSTEM, MASTER DIAMONDS, RIVER-TO-LIGHT-YELLOW SYSTEM.
Last Updated ( Friday, 14 September 2007 )
 
colored diamonds PDF Print E-mail
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Friday, 14 September 2007
colored Diamonds. Referred to as "fancy stones" or "fancy diamonds" in the trade, they occur in yellow, brown, pink, red, blue and green. The color is believed to be the result of defects in the crystal lattice (color centers). See FANCY diamond, COLOR CENTER.
 
color change PDF Print E-mail
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Friday, 14 September 2007
color change. A diamond's color that has been changed either perma¬nently or temporarily as a result of exposure to heat or certain kinds of radiation. See CYCLOTRON-TREATED DIAMOND, ELECTRON-BOMBARDED DIAMOND, FLUORESCENCE, FLUOROCHROMATIC, PILE-TREATED DIAMOND, PHOSPHORESCENCE, RADIO ISOTOPE, TRANSICHROMATIC.
 
color center PDF Print E-mail
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Friday, 14 September 2007
color center. A structural defect in the atomic lattice of a mineral that absorbs light. There are various types of color centers; for example, the F center causing the purple color in fluorite which consists of a negative ion vacancy combined with an elec¬tron. Irradiated blue Diamonds are due to a color center and do not conduct electricity. See COLORED DIAMONDS.
 
Colorado PDF Print E-mail
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Friday, 14 September 2007
Colorado. To date, approximately 12 small (about 2 mm. in diameter) Diamonds have been discovered from kimberlite pipes in Colorado. They were all recovered in 1975 from the Sloan diatremes (1 and 2) in Section 10, T. 10 N., R. 72 W., Larimer County, Colorado. Colorado diamond. A misnomer for transparent smoky quartz.
 
Collis Diamond Syndicate PDF Print E-mail
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Friday, 14 September 2007
Collis diamond Syndicate. A syndi¬cate formed in 1906 to finance an expedition to the islands off the coast of South-West africa. A vessel named the Xema was chartered to take out 45 men to dig for Diamonds. The expedition failed, because the Cape Government, to whom the is¬lands belonged, prevented any land¬ing.
 
Collins PDF Print E-mail
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Friday, 14 September 2007
Collins, S. V. American oil man and entrepreneur who formed the Marine diamond Corporation to exploit a 170-mile offshore mining concession off the coast of Southwest africa from the Orange River to Luderitz in 1962. A prospecting ship, the Rock-eater, drilled out the sea-bed to locate the payable areas. After the Rock-eater found the diamond-bearing gravels, a recovery barge for under¬sea Diamonds, the 300-foot long barge Pomona, was towed to the site to extract the diamonds. The Pomo¬na has powerful suction dredges which draw the gravels into the barge to be separated and concen¬trated by normal methods. The com¬pany is no longer extant.
 
collet PDF Print E-mail
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Friday, 14 September 2007
collet. (1) Same as culet. (2) The metal portion of a finger ring in which a stone is set.
 
collection color PDF Print E-mail
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Friday, 14 September 2007
collection color. (1) A color grade term used in the color classification of rough Diamonds at the source by the diamond Trading Co. for the second best color or the first two finest colors mixed together. (2) Extra collection is the finest color. (3) This term, as well as collection blue and collection gem blue, is used by some importers and retailers as color grades for colorless diamonds and, unethically, for those tinged with yel¬low. collection gem blue. See COLLECTION COLOR,
Last Updated ( Friday, 14 September 2007 )
 
Colesberg Kopje PDF Print E-mail
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Friday, 14 September 2007
Colesberg Kopje. An early synony¬mous term for the De Beers New Rush. See NEW RUSH, KIMBERLEY MINE.
 
Colenso Diamond PDF Print E-mail
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Friday, 14 September 2007
Colenso diamond. In 1887, John Ruskin gave a large diamond crystal to the British Museum of Natural His¬tory in honor of his friend, John Wil¬liam Colenso, distinguished mathema¬tician and first bishop of Natal, Re¬public of South africa. The crystal, described as a fine-quality, 133-carat yellowish octahedron was stolen from the Museum in 1965 and never recovered.
 
Cognac Over Ice Diamond PDF Print E-mail
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Friday, 14 September 2007
Cognac Over Ice diamond. This rare 34-carat cognac colored, pear-shaped diamond, owned by Eliza¬beth Taylor, is unofficially called "Cognac Over Ice." Reportedly, it was bought in Geneva, in January, 1974, by Richard Burton from the private collection of Mr. Arpels of Van Cleef and Arpels in Geneva.
 
coated diamond PDF Print E-mail
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Friday, 14 September 2007
coated diamond. A diamond that has been coated on the pavilion or gir¬dle, or entirely, with a substance that imparts a bluish color and masks a yellowish body color. Although such treatment improves color, it is a de¬ceptive practice. Also called painted diamond. A person who is skilled in the art of coating or painting dia¬monds is sometimes referred to as a diamond "artist."
 
coated crystal PDF Print E-mail
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Friday, 14 September 2007
coated crystal. A diamond crystal, usually alluvial, that has a coating of mineral matter. Typically, a clear stone is covered with a layer of trans¬lucent green material with a rough surface resembling a green-orange skin, the coating being as much as two or three millimeters thick, the average is about one-half millimeter. The coating varies in color from light greenish-gray through light yellow-green, olive green and dark green. The tone of the color may well vary with the thickness of the coating.
 
coal-oil blue PDF Print E-mail
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Friday, 14 September 2007
coal-oil blue. A trade term referring to yellow Diamonds that have an oily-bluish body appearance in day¬light. The effect is caused by strong fluorescence. See PREMIER diamond.
 
cluster PDF Print E-mail
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Friday, 14 September 2007
cluster. A group of closely set stones. Sometimes, they are arranged to im¬part the illusion of a single larger stone.
 
cloverleaf effect PDF Print E-mail
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Friday, 14 September 2007
cloverleaf effect. The appearance seen around the culet of a brilliant-cut diamond, the pavilion of which has been subjected to the beam of deuterons or alpha particles in a cy¬clotron to impart a green color to the stone. Since the penetration of such particles is not great, and the color is concentrated at the maximum depth of penetration, the zone of color forms a scalloped "halo" around the culet that has been likened to the shape of a cloverleaf. It is also some¬times referred to as an "umbrella" ef¬fect. See CYCLOTRON TREATED DIAMOND.
 
cloud PDF Print E-mail
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Friday, 14 September 2007
cloud (or cloudy texture). A group of tiny white inclusions in a diamond that together give a cottony or clouded appearance in the otherwise highly transparent stone. A cloud may be so minute that it is difficult to see under 10x, or it may be large enough to deprive the entire stone of brilliancy.
 
close goods PDF Print E-mail
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Friday, 14 September 2007
close goods. A grading term used at the mines for diamond crystals of good color and symmetry and free from imperfections.
 
closed table PDF Print E-mail
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Friday, 14 September 2007
closed table. A term used by some diamond men to designate a small table diameter. However, its interpre¬tation and use varies. It may refer to a diameter less than the American cut 53% (of the girdle diameter) or, more frequently, to a table smaller than about 60%, because so many of the stones cut today have tables well over that figure. See TOLK6WSKY THEORETICAL BRILLIANT CUT; PROPORTIONS, GOOD; SPREAD stone; TABLE; TABLE SIZE.
 
closed setting PDF Print E-mail
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Friday, 14 September 2007
closed setting. Dating from Renais¬sance times, the closed setting was a rim to hold the stone closely with an enclosed base.
 
closed culet PDF Print E-mail
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Friday, 14 September 2007
closed culet. A culet that is too small to be resolved with the unaided eye and that can be seen only with diffi¬culty under 10x. The term is rarely used to refer to a pavilion point or ridge with no culet. See BRILLIANT CUT (ROUND), CULET, OFF-CENTER CULET, OPEN CULET
 
Clinch River Diamond PDF Print E-mail
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Friday, 14 September 2007
Clinch River diamond. Unofficial name. 3 carats. Found in 1889 on Clinch River, Roane Co., Tennessee. Whereabouts not known.
 
Cleveland Diamond PDF Print E-mail
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Friday, 14 September 2007
Cleveland diamond. The Cleveland Diamond is thought to have been the first large diamond cut in New York City. This 50-carat, 128-facet cush¬ion-shaped stone was fashioned from a 100-carat crystal by S. Dessau of Maiden Lane in I884. The stone was named in honor of Grover Cleveland, who had just been elect¬ed the twenty-second president of the United States. Minnie Palmer, musical-comedy star of the 1880's, wore it hidden inside a large flower brooch that parted on touch to reveal the gem. It is not known where this stone is today.
 
Cleveden PDF Print E-mail
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Friday, 14 September 2007
Cleveden. A minor alluvial diamond deposit in the Herbert area, Cape Province, Republic of South africa. Present production from this deposit is of little consequence.
 
cleaving PDF Print E-mail
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Friday, 14 September 2007
cleaving. A process occasionally used in fashioning Diamonds and, but rarely, other stones; the splitting of a stone along a cleavage plane, or grain, into two or more portions, to produce pieces of a size or shape that will produce fashioned stones more economically or of better qual¬ity.
 
cleaver's mallet PDF Print E-mail
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Friday, 14 September 2007
cleaver's mallet. A rounded wooden mallet that is used to strike the cleaver's knife to cleave a diamond. cleaver's stick. The holder either for the diamond being cleaved or for the sharp being used to dig the groove or kerf preparatory to the cleavage op¬eration.
 
cleaver's knife PDF Print E-mail
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Friday, 14 September 2007
cleaver's knife (or blade). A wedge-shaped steel knife used for cleaving Diamonds.
 
cleaver PDF Print E-mail
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Friday, 14 September 2007
cleaver. The workman who prepares and cleaves Diamonds. Also he is often responsible for planning the en¬tire fashioning from the rough.
 
cleavage PDF Print E-mail
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Friday, 14 September 2007
cleavage. (1) The tendency of a crys¬talline mineral to break in certain def¬inite directions, parallel to a possi¬ble crystal face, leaving a more or less smooth surface. (2) Any break along the grain of a diamond parallel to one of four pairs of octahedral faces. (3) The act or process of pro¬ducing such a break. (4) One of the portions of a diamond resulting from such a break. (5) A term sometimes used for a diamond crystal that re¬quires cleaving before being fashioned. (6) A misshapen diamond crystal, particularly one that is flat and rather elongated. The term is used by diamond cutters to refer to such a crystal, whether or not its form results from cleaving. (7)
Last Updated ( Friday, 14 September 2007 )
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clean PDF Print E-mail
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Friday, 14 September 2007
clean. A term used by some jewelers to mean absence of internal imper¬fections only, and by others to de¬scribe Diamonds with slight imper¬fections. It is prohibited by the American Gem Society for use by its members. It is also prohibited by the Federal Trade Commission, unless the stone meets the Commission's definition of the term perfect. See PER¬FECT.
 
claw setting PDF Print E-mail
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Friday, 14 September 2007
claw setting. A setting favorable for transparent faceted stones which al¬lows more light to enter the stone. The stone is gripped just above the girdle by projecting metal claws.
 
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