A mineral that consists essentially of crystallized carbon according to the isometric crystal system, with a hardness of 10 on Mohs scale, a density of 3.52 and a refractive index of about 2.42, and created by nature. (Note: the term 'diamond' without further clarification always implies 'natural diamond')
An artificial product that essentially has the same chemical composition, crystal structure, and physical (including optical) characteristics as a diamond.
A diamond that underwent human intervention to temporarily or permanently change its appearance. Do not include: cutting, grinding, cleaning and setting. Examples of this include: optical coatings, filler fails, pressurized heating, irradiation, laser drilling, high pressure and high temperature (HPHT) treatment or any other physical or chemical process.
The weight of a diamond is expressed in carats. One carat equals 0,2 gr. or 100 points, which indicates the size.
Most diamonds range in colour from colourless to slightly yellow. The colour grade is determined by comparison with a series of master stones, the best grade being colourless – a perfect diamond has no colour at all (D Colour: Exceptional White+). Diamonds can also occur in all ranges of colours, from brownish to striking yellow, pink, purple, red, blue and green. These are called ‘fancy colours’. Some diamonds react to UV-light (black light) with a grading scale for fluorescence, which ranges from ‘nil’, ‘slight’, or ‘medium’ to ‘strong’.
With clarity, ce describe a diamond’s purity. As they are a product of nature, all natural diamonds have traces of their growth history. In most gem quality diamonds these are minor internal characteristics or inclusions. The clarity scale reflects the size, number and location of the characteristics when examined with a 10x loupe. Diamonds that have no inclusions visible to the naked eye are of excellent quality. The very best – and rarest clarity is called ‘loupe clean’. This means that upon examining the diamond with a loupe, no inclusions can be found.
A diamond’s cut is essential to its beauty. The cut is divided into 3 grades: proportion, polish and symmetry. Each grade is evaluated according to four parameters: Excellent, Very Good, Good and Fair. A perfect cut equals more sparkle, brilliance and fire.
- Proportions determine the brilliance and ‘fire’ of a diamond.
- Symmetry describes the variation of different parameters that define the proportions.
- Polish describes the finish of the facets.