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Diamond certified FL (flawless) by the GIA Two diamonds of grade VS 1 and SI 2 respectively. The GIA diamond grading scale is divided into six categories and eleven grades. [2] The clarity categories and grades are: [3] Flawless category (FL) diamonds have no inclusions or blemishes visible under 10× magnification. [3]
In 1953 the GIA developed its International Diamond Grading System and the "four Cs" (cut, clarity, color, and carat weight) as a standard to compare and evaluate the quality of diamonds. [2] As of 2024, the institute is headquartered in Carlsbad, California, and operates in 13 countries, with 11 campuses, 9 laboratories, and 4 research centers.
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IGI provides independent grading reports, colored stone reports, identification and appraisal reports, diamond authentication and attestations of origin, and laser inscription services. They also offers diamond and colored stone courses through IGI's Schools of Gemology. [7] Graduates from the IGI school of Gemology are awarded an IGI Diploma.
Type II diamonds have very few if any nitrogen impurities. Pure (type IIa) diamond can be colored pink, red, or, brown owing to structural anomalies arising through plastic deformation during crystal growth; [20] these diamonds are rare (1.8% of gem diamonds), but constitute a large percentage of Australian diamonds. Type IIb diamonds, which ...
This is a partial list of the largest non-synthetic diamonds with a rough stone (uncut) weight of over 200 carats (40 grams). [1] The list is not intended to be complete—e.g., the Cullinan (formerly Premier) mine alone has produced 135 diamonds larger than 200 carats since mining commenced.
The short B-N (1.57 Å) bond is close to the diamond C-C bond length (1.54 Å), that results in strong covalent bonding between atoms in the same fashion as in diamond. The slight decrease in covalency for B-N bonds compared to C-C bonds reduces the hardness from ~100 GPa for diamond down to 48 GPa in c-BN.
Synthetic diamonds of various colors grown by the high-pressure and high-temperature technique, the diamond size is ~2 mm. Infrared absorption spectrum of type IaB diamond. (1) region of nitrogen impurities absorption (here mostly due to the B-centers), (2) platelets peak, (3) self-absorption of diamond lattice, (4) hydrogen peaks at 3107 and ...
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