The name diamond is derived from the Greek adamas = the indomitable.
Diamonds were formed at a depth of about 80 km at high temperatures and pressures in volcanic explosion vents. Diamond is the hardest natural material. It has a hardness of 10 on the Mohs scale. Its Rosiwal hardness (also known as absolute hardness) is 140 times greater than that of corundum.
The brilliant cut diamond:
Various brilliant cuts have been developed until the proportions of the ideal diamond were finally established. The brilliant cut means a round shape with at least 32 facets in the upper part (table not included) and at least 24 facets in the lower part (culet not included).
Only the diamond may be named without the brilliant. All other stones must also be marked with their mineral name, e.g. ruby in brilliant cut.
To be able to evaluate the diamond, one must know the 4 "C's":
Colour = Colour
There is an international agreement on the colour of diamonds, published in Germany under the name RAL 560 A 5 E. There is also an American classification. There is also an American classification (GIA) and a CIBJO proposal.
High Fine White+ (River), GIA designation: D
High Fine White (River), GIA designation: E
Fine White+ (Top Wesselton), GIA designation: F
Fine White (Top Wesselton), GIA denomination: G
White (Wesselton), GIA denomination: H
Lightly tinted white+ (Top Crystal), GIA designation I
Light tinted white (Top Crystal), GIA designation J
White tinted+ (Crystal), GIA denomination: K
Tinted White (Crystal), GIA denomination: L
Tinted 1 (Top Cape), GIA denomination: M, N
Tinted 2 (Cape), GIA designation: O
Clarity = Purity
The clarity of a diamond is the internal purity of the mineral. Clarity can be affected by ingrown minerals, cracks and signs of growth. These are collectively known as inclusions. Cut diamonds are considered flawless if they show no inclusions when magnified ten times with an achromatic and aplanatic loupe.
Cut = polish
The sparkle of a brilliant-cut diamond depends largely on the cut. The value of a cut diamond also depends on the quality of the cut.
This includes the shape, type, proportion, symmetry and external characteristics of the cut.
In Germany, the standard is the "fine-cut diamond", i.e. its cut data deviates only slightly from that of the ideal diamond.
The following cut grading table applies to brilliant-cut diamonds under 1 carat and is published as RAL 560 A 5 E:
Very good, excellent brilliance, few or minor external features, very good proportions.
Good, good brilliance, some external features, proportions with minor deviations
Medium, reduced brilliance, several important external features, proportions with considerable deviations
Poor, significantly reduced brilliance, large and/or numerous external features, proportions with very significant deviations.
Carat = weight
Carat is the unit of weight in the gemstone trade, as opposed to carat, which is used to describe the fineness of precious metals.
The term carat, from the Greek keration = small horn, has several roots. The most common derivation is believed to be from the Latin name of the carob tree, Ceratonia Siliqua, whose seeds weigh an average of 197 milligrams.