Cut refers not only to a diamonds shape (e.g. round, oval, pear, etc.) but to a diamonds proportions, symmetry and polish. Many gemmologists consider the cut of a diamond to be its most important characteristic. The beauty of a diamond depends more on cut than any other factor. Though extremely difficult to analyse and quantify, diamond cut has three primary effects on appearance: brilliance (the brightness created by the combination of all the white light reflections from the surface and the inside of a polished diamond), fire (the dispersion of light into the colours of the visible spectrum, seen as flashes of colour), and scintillation (the flashes of light and dark, or sparkle, when a diamond or light source is moved). In other words, a diamond with a poor cut will appear dull, even if it has the perfect colour and clarity.
See Diagram below.
Because they are formed deep within the earth under extreme heat and pressure, virtually all diamonds contain "birthmarks"; small imperfections inside the diamond (called inclusions), or on its surface (called blemishes). Clarity refers to the degree to which these imperfections are present. Diamonds which contain numerous or significant inclusions or blemishes have less brilliance because the flaws interfere with the path of light through the diamond.
See Diagram below.
Please note P1 - 3 & I1 - 3 are exactly the same
When it comes to a diamonds colour, many people think that a "good" colour means that it is brilliantly white - but this is seldom the case. Nature has provided a whole spectrum of colours in the makeup of diamonds, including red, pink, green, blue, and yellow. Acting as a prism, a diamond divides light into a spectrum of colours and reflects this light as colourful flashes called fire. The less colour in a diamond means the more colourful the fire, which results in a better colour grade.
The photo below shows a master set used by gemmologists to grade colour in diamonds. Each diamond to be graded is compared to the master set to determine where it should fall on the diamond colour scale. The colours you see below are slightly exaggerated, since viewing diamonds face down makes their body colour more pronounced. The face down orientation makes the detection of body colour easier because brightness and fire are minimized when the diamond is face down.
A diamond or gemstones "Carat" designation is a measurement of both the size and weight of the stone. One "Carat" is a unit of mass that is equal to 0.2 grams (200 milligrams). A carat can also be divided into "points" with one carat being equal to 100 points, and with each point being 2 milligrams in weight. Therefore, a 1/2 carat diamond would be 50 points, a 3/4 carat diamond is 75 points, and a 2 carat diamond is 200 points.When a single piece of jewellery has multiple stones, the total mass of all diamonds or gemstones is referred to as "Total Carat Weight" or "T.C.W."
Two diamonds of equal carat weight may also appear very different in size based on the shape of the diamond. For instance, a 1 carat marquise tends to appear larger than a 1 carat round. The chart below illustrates why. For each diamond, the chart shows the following:
- Approximate size. The diamond images shown are a very close approximation of the actual size of a 1 carat excellent cut for each shape. Visually, the longer shapes (oval, marquise, pear, emerald) tend to appear larger to the eye than the round and square shapes.
- Measurements (Length x Width). The measurements correspond to the shape shown above, and are typical for excellent cut diamonds of 1 carat weight.
- Crown Area - The total surface area (mm2). The area gives the true size of the diamond face up (as it would appear when set in a ring). For example, while the oval diamond image appears larger than the round image, the actual surface area is the same for the two shapes, meaning the difference in size is one of perception, not reality. In contrast, the oval not only appears larger than the princess cut, it actually has a larger surface area (approximately 10% larger in this example), meaning the difference is not simply an illusion created by the elongated shape.
Remember that while the measurements below are typical, every diamond is unique.
A black diamond, or Carbonado originated on earth 3.5 billion years ago. Infernal heat and pressure, under the earths surface transformed the carbon atoms into crystals. Black Diamonds are opaque and just like colour-less diamonds, they are of great hardness that amounts to 10 in the Mohss scale of hardness.
Black Diamonds are full of criss-crossing inclusions containing black deposits of Sulphides which are responsible for their opaque texture. Pitting on the stones surface may also be evident and is quite normal.
As a general rule, black diamonds contain a multitude of grey and dark grey elements the combination of which form the black colour.
Diamonds that naturally occur with shades of colour are referred to as "Fancy". Fancy coloured diamonds are valued by the intensity of their colour concentration. All coloured diamonds belong to the carbon family. The difference of the colour is the result of the different molecular structures of the crystals.
Black diamonds are often enhanced and are still genuine diamonds treated with radiation to make their colour appear more black, or to obtain uniform colour.
It is typically much better quality than a "natural" black diamond due to the nature of its inclusions.
In ancient Italy, a black diamond was regarded as the stone of reconciliation. It was believed that touch of black diamond has the power of patching up all misunderstandings between the warring couples.