All rough diamonds have ‘birthmarks’, or imperfections, that were created during the long natural formation process. These birthmarks may be located inside the diamond, where they are known as inclusions, or on the outer surface of the rough diamond, called flaws. There are many different types of inclusions and flaws. Here are some of the most common types:
Clouds: Internal inclusion that has a hazy, cloudy appearance. Often caused by a cluster of pinpoint inclusions close together.
Crystals: The presence of small crystals or minerals often occurs naturally in diamonds.
Feathers: Internal inclusions caused by small cracks sometimes take on a feathery appearance.
Graining: Sometimes crystal inclusions form in a line that appears grainy. These lines make the polishing process more difficult as the diamond must always be cut against the grain.
Naturals: Flaws on the surface that were left untouched by the diamond cutter are known as naturals. These are often a sign of good cutting practice, as the diamond cutter has minimized the weight loss of the original rough diamond.
Blemishes: Blemishes appear on the diamond surface. They may occur naturally but are more often caused by external factors during the cutting process.
Scratches: These are fine lines on the diamond’s surface. They may occur naturally or may be a result of the cutting process.
Pits: Small indentations on the diamond surface may take on the appearance of pitting.
Nicks: Tiny chips of the diamond surface are known as nicks. Nicks can be removed during the cutting process by adding facets, however this may also reduce the diamond’s brilliance.
The size, location and number of inclusions and flaws greatly affect the way the diamond will be cut and polished. Flawless diamonds – those without inclusions or surface flaws – are rare and highly valuable.