Informations
Diamonds
Diamond: A unique stone amongst all
Diamonds are the most precious objects most people will ever see: A stone you can cradle in your palm can be worth more than the biggest house in a good-sized town.
They always have been valuable. In the first century A.s.., the Roman naturalist Pliny said: ‘Diamond is the most valuable, not only of precious stones, but of all things in this world’. One sixteenth century Indian Sultan had a diamond he valued at ‘half a daily expense of the whole word’.
The word "diamond" comes from the Greek word adamas, meaning "unconquerable", due to its incomparable hardness.
Over the years, diamond professionals have developed precise standards for comparing or grading the characteristics of individual diamonds and setting their values. These reflect, among other things, the rarity of certain characteristics, a consensus of expert opinion regarding beauty and quality. This is why a precise analyse of a diamond may only be done by a graduate gemmologist.
Where do they come from?
The Great Moguls of India who were the first to discover large quantities of diamonds in their territories, contracted huge fortunes through these gems. It was not until the 17th century that Europe showed a great enthusiasm for these stones, that only the wealthiest could afford. It is only when they began to run out of deposits, that the European nations had the ground searched by their recent colonies to uncover a new source of wealth.
In the mid-18th century, many thought that we had exhausted the world supply of diamonds. Then in 1866 the first diamond in South Africa, the Eureka, was discovered and a new rush began.
The four C’s : your key to understanding diamond value.
CUT
Cut is the human contribution to a diamond’s beauty, and has important effects on each of the other 4 C’s; it can both enhance color and hide inclusions. It ensures that a given stone has maximum brilliance and sparkle which would not be the case were the stone cut for weight alone. A round, brilliant cut, diamond has 57 to 58 facets. 
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COLOR
Diamond is the only gem in which an absence of color means it is more valuable. Although most diamonds are thought to be colorless, they usually run from very nearly colorless to slightly yellow, brown, or gray- the normal range.
But diamonds occur in every color of the rainbow (few are rarely colorless). Diamonds with distinct tints other than those of the normal color range (and yellow, brown, and gray diamonds with color deep enough to be attractive) are classed as fancy colors. With the exception of rare fancy colors such as blue, pink and red, colorless diamonds still command the highest prices.
However, diamonds can be color-treated in several ways. The most common methods employ irradiation (completely safe for the wearer), or a combination of irradiation and heat. Normally this produces a permanent color change and is more affordable than a natural colored diamond. An irradiated stone should always be clearly identified as a treated diamond.
The Gemological Institute of America (GIA), which is an international reference, rates the body color in white diamonds from D (colorless) to Z (light yellow). 
CLARITY
The clarity of a diamond relates to exactly how clear a diamond is. It describes the presence, or absence, of Inclusions (flaws) within the diamond and any blemishes on its surface. Diamonds are graded for clarity under 10x loupe magnification. Grades range from Flawless (diamonds which are completely free of blemishes and inclusions), to Included 3 (diamonds which possess large, heavy blemishes and inclusions that are visible to the naked eye).
Keep in mind that for grades F through SI, a diamond's clarity grade has an impact on the diamond's value, not on the unmagnified diamond's appearance.
FL (Flawless): Reveal no flaws on the surface or internally are the rarest and most beautiful gems.
IF (Internally Flawless): Reveal no inclusions and only insignificant blemishes on the surface under 10x magnification.
VVS1 - VVS2 (Very, Very Slightly Included): Very difficult to see inclusions under 10x magnification. These are excellent quality diamonds.
VS1 - VS2 (Very Slightly Included): Only looking through a 10X loupe can pinpoint the inclusions in this category and are nearly impossible to see with the naked eye. These are less expensive than the VVS1 or VVS2 grades.
SI1 - SI3 (Slightly Included): Diamonds with inclusions easily identified under 10x magnification. Finding flaws in this category with the naked eye is difficult. The gems in this category maintain their integrity, depending on the location of the inclusions.
I1 - I3 (Included): Diamonds with inclusions which may or may not be easily seen by the naked eye. The flaws on the stones in this category will have some effect on the brilliance of your diamond.
CARAT (weight)
A diamond’s weight is measured in carats (1 carat = 100 points). The carat is divided into hundredths, which is also called 'points': for example, a diamond that weighs 0.25 carat equals 25 points or 1 / 4 carat. The weight alone can never determine the value of a diamond.The price of a diamond is not proportional to its weight. Since larger stones are more rare in nature, they are more expensive as well. For instance, one diamond weighing 2 carats will always cost much more than two diamonds of the same quality weighing 1 carat each.