In mineralogy, diamond (/daɪᵊmənd/; from the ancient Greek ἀδάμας – adámas "unbreakable").Most natural diamonds are formed at high temperature and pressure at depths of 140 to 190 kilometers (87 to 118 mi) in the Earth's mantle. Carbon-containing minerals provide the carbon source, and the growth occurs over periods from 1 billion to 3.3 billion years (25% to 75% of the age of the Earth). Diamonds are brought close to the Earth's surface through deep volcanic eruptions by a magma, which cools into igneous rocks known as kimberlites and lamproites.
Typically diamonds are priced by a combination of four major factors:
The cut of a diamond typically refers to the different shapes on offer. These vary and the following are the most well known in the world market and have been available for many years: ROUND BRILLIANT, PRINCESS, RADIANT, ASSCHER, CUSHION, OVAL, MARQUISE, PEAR, EMERALD and HEART.
Thereafter, and very importantly, the cut of a diamond refers to the angles, dimensions and proportions in which the diamond has been cut. Every effort is made in the manufacturing process to cut the diamonds according to world standards of brilliance, to allow the finished product to show the maximum amount of light to reflect through the top of the diamond, allowing for great shine and brilliance.
Clarity refers to the imperfections or “flaws” within a diamond. Typically diamond clarity and its description has become standardised by all major diamond laboratories as follows:
IF- INTERNALLY FLAWLESS, no flaws or imperfections.
- VVS1 – very, very slight inclusion 1
- VVS2 – very, very slight inclusion 2
- VS1 – very slight inclusion 1
- VS2 – very slight inclusion 2
- SI1 – slight inclusion 1
- SI2 – slight inclusion 2
- Si3 – slight inclusion 3
- I1 – inclusion 1
- I2 – inclusion 2
- I3 – inclusion 3
Thereafter the colour range drops down alphabetically illustrating less “PURE WHITE” and slighlty more colour, in most cases more yellow all the way down to “Z”. After “Z” colour, diamonds can be descibed as “FANCY” in their intensity of shade, i.e. YELLOW, PINK, BLUE etc. Fancy colours are less common than “whiter diamonds” and in many instances can become collectors’ items).
Diamond color is all about what you can’t see. Diamonds are valued by how closely they approach colorlessness – the less color, the higher their value. (The exception to this is fancy color diamonds, such as pinks and blues, which lie outside this color range.) Most diamonds found in jewelry stores run from colorless to near-colorless, with slight hints of yellow or brown.
GIA’s color-grading scale for diamonds is the industry standard. The scale begins with the letter D, representing colorless, and continues with increasing presence of color to the letter Z, or light yellow or brown. Each letter grade has a clearly defined range of color appearance. Diamonds are color-graded by comparing them to stones of known color under controlled lighting and precise viewing conditions.
Many of these color distinctions are so subtle as to be invisible to the untrained eye. But these slight differences make a very big difference in diamond quality and price.
WHY DOES THE GIA COLOR GRADING SYSTEM START AT D?
Before GIA developed the D-Z Color Grading Scale, a variety of other systems were loosely applied. These included letters of the alphabet (A, B and C, with multiple A’s for the best stones), Arabic (0, 1, 2, 3) and Roman (I, II, III) numerals, and descriptions such as “gem blue” or “blue white.”
The result of all these grading systems was inconsistency and inaccuracy. Because the creators of the GIA Color Scale wanted to start fresh, without any association with earlier systems, they chose to start with the letter D—a letter grade normally not associated with top quality.
In earlier times diamonds were measured in weight using carob seeds. These small seeds had a fairly uniform weight and traders would use them as counterweights to balance their scales. Ultimately a stone of a certain size became equal to one carob seed and finally a 1 carat diamond. For diamonds under 1 carat: a carat is divided into 100 points. i.e. 0.50 points (half a carat); 0.75 points(3/4 of a carat).