The most familiar use of diamonds today is as gemstones used for adornment, a use which dates back into antiquity.
Gold is a highly sought-after precious metal which, for many centuries, has been used as money, a store of value and in jewelry. The metal occurs as nuggets or grains in rocks, underground "veins" and in alluvial deposits. It is one of the coinage metals. Gold is dense, soft, shiny and the most malleable and ductile of the known metals. Pure gold has a bright yellow color traditionally considered attractive.Excellent optical and mechanical properties, combined with efficient marketing, make diamond the most popular gemstone.
The dispersion of white light into spectral colors is the primary gemological characteristic of gem diamonds. In the 20th century, experts in gemology have developed methods of grading diamonds and other gemstones based on the characteristics most important to their value as a gem. Four characteristics, known informally as the four C's, are now commonly used as the basic descriptors of diamonds: these are carat, cut, color, and clarity. A large, flawless diamond is known as a paragon.
Diamond is the hardest natural material known, where hardness is defined as resistance to scratching and is graded between 1 (softest) and 10 (hardest) using the Mohs scale of mineral hardness. Diamond has a hardness of 10 (hardest) on this scale.
The hardness of diamond contributes to its suitability as a gemstone. Because it can only be scratched by other diamonds, it maintains its polish extremely well. Unlike many other gems, it is well-suited to daily wear because of its resistance to scratching-perhaps contributing to its popularity as the preferred gem in engagement or wedding rings, which are often worn every day.
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.
In order of rarity, colorless diamond, by far the most common, is followed by yellow and brown, by far the most common colors, then by blue, green, black, translucent white, pink, violet, orange, purple, and the rarest, red.
"Black", or Carbonado, diamonds are not truly black, but rather contain numerous dark inclusions that give the gems their dark appearance. Colored diamonds contain impurities or structural defects that cause the coloration, while pure or nearly pure diamonds are transparent and colorless. Most diamond impurities replace a carbon atom in the crystal lattice, known as a carbon flaw. The most common impurity, nitrogen, causes a slight to intense yellow coloration depending upon the type and concentration of nitrogen present. The Gemological Institute of America (GIA) classifies low saturation yellow and brown diamonds as diamonds in the normal color range, and applies a grading scale from "D" (colorless) to "Z" (light yellow). Diamonds of a different color, such as blue, are called fancy colored diamonds, and fall under a different grading scale.
Diamonds can be identified by their high thermal conductivity. Their high refractive index is also indicative, but other materials have similar refractivity. Diamonds cut glass, but this does not positively identify a diamond because other materials, such as quartz, also lie above glass on the Mohs scale and can also cut it.
A large trade in gem-grade diamonds exists. Unlike other commodities, such as most precious metals, there is a substantial mark-up in the retail sale of gem diamonds.
Source: Diamond. (2010, September 28). In Wikipedia, The Free Encyclopedia. Retrieved 08:47, September 28, 2010 from http://en.wikipedia.org/wiki/Diamond
Diamond clarity is a quality of diamonds relating to the existence and visual appearance of internal characteristics of a diamond called inclusions, and surface defects called blemishes. Clarity is one of the four C's of diamond grading, the others being carat, color, and cut.
Inclusions may be crystals of a foreign material or another diamond crystal, or structural imperfections such as tiny cracks that can appear whitish or cloudy. The number, size, color, relative location, orientation, and visibility of inclusions can all affect the relative clarity of a diamond. A clarity grade is assigned based on the overall appearance of the stone under 10x magnification.
The GIA diamond grading scale is divided into six categories and eleven grades. The clarity categories and grades are:
Diamond testing and Diamond value