31 March 2014
DIAMOND - Its Features
In mineralogy, diamond (from the ancient Greek αδάμας – adámas "unbreakable") is a metastable allotrope of carbon, where the carbon atoms are arranged in a variation of the face centered cubic crystal structure called a diamond lattice. Diamond is less stable than graphite, but the conversion rate from diamond to graphite is negligible at standard condition. Diamond is renowned as a material with superlative physical qualities, most of which originate from the strong covalent bonding between its atoms. In particular, diamond has the highest hardness and thermal conductivity of any bulk material. Those properties determine the major industrial application of diamond in cutting and polishing tools and the scientific applications in diamond knives and diamond anvil cells.
The Gemological Institute of America, or GIA, is a nonprofit institute dedicated to research and education in the field of gemology and the jewelry arts. Founded in 1931, GIA's mission is to protect all buyers and sellers of gemstones by setting and maintaining the standards used to evaluate gemstone quality. The institute does so through research, gem identification and diamond grading services and a variety of educational programs. Through its world-renowned library and subject experts, GIA acts as a resource of gem and jewelry information for the trade, the public and worldwide media outlets.
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.
Today, the institute is headquartered in Carlsbad, California and operates out of 14 countries, with 12 campuses, seven laboratories and four research centers worldwide.
Synthetic diamonds are diamonds manufactured in a laboratory, as opposed to diamonds mined from the Earth. The gemological and industrial uses of diamond have created a large demand for rough stones. This demand has been satisfied in large part by synthetic diamonds, which have been manufactured by various processes for more than half a century. However, in recent years it has become possible to produce gem-quality synthetic diamonds of significant size It is possible to make colorless synthetic gemstones that, on a molecular level, are identical to natural stones and so visually similar that only a gemologist with special equipment can tell the difference
The majority of commercially available synthetic diamonds are yellow and are produced by so-called High Pressure High Temperature processes.The yellow color is caused by nitrogen impurities. Other colors may also be reproduced such as blue, green or pink, which are a result of the addition of boron or from irradiation after synthesis.
Most diamonds are cut round with a full 58 facets, and a good cut, or make, has more scintillation, more sparkle. It is the work of a master cutter that allows the diamond to be cut in such a way as to permit the maximum amount of light to be reflected through the diamond, and that's a great reflection on you. It is the cut that enables a diamond to make the best use of light.
The most common diamond color is yellow. Most diamonds have a slight hint of yellow and the diamond color scale is based on the amount of yellow present in a diamond. Diamond color is graded according to the GIA Grading Scale. Grades are based on the amount of yellow that is visible when viewed facedown through the pavilion on a white diamond color card using daylight equivalent fluorescent light.
The diamond's clarity is a description of its internal purity. With fewer imperfections within the stone, the diamond is rare and has a higher value. The clarity scale was developed by the Gemological Institute of America (GIA) to quantify these imperfections. The American Gem Society (AGS) uses the same standards as the GIA; however, the AGS uses a numerical system where "0" is the cleanest (GIA "IF") and "10" is the most imperfect (GIA "I3").
A carat is a weight measuring unit equal to 0.2 grams. It is the internationally used unit to measure the weight of diamonds. Within the diamond trade, fractions of a carat are referred to as "points" or simply as fractions. A 50-point diamond weighs 0.5 carats or 1/2 a carat. A 1-carat diamond weighs 100 points. A 1/3 is also 0.3 carats or 30 points.
Posted by Anonymous on March 31, 2014