Hearts & Arrows
Explore the diamond’s hidden symmetry.
The vast majority of diamonds found on our planet were formed much deeper in the earth’s interior than most other minerals, at depths of over 140 km and temperatures of 900 to 1400°C in the upper mantle. They were formed in deep rocks such as eclogite and peridotite, and were brought close to the earth’s surface by volcanic magma. Diamonds are not found in the rock in which they formed, but rather in the rock in which they were transported, namely Kimberlite and Lamproite.
Diamonds are mined either directly from the rock, in primary deposits, or secondary deposits, where diamonds are found in soil, gravel or sand. Secondary deposits are created by erosion of primary rocks and transported by water; hence transported diamonds are found in river beds, at beaches or in the sands of the ocean floor.
Rough diamonds are mined diamonds in their natural state, before any processing or polishing has occured.
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.