Clarity refers to diamond’s purity and is determined by presence or absence of internal or surface impurities (often called inclusions). Most of naturally formed diamonds have some imperfections in their structure, which is normal given diamonds growth process. For example, small crystals can become trapped in a diamond when it is forming. Sometimes diamond when it grows can develop irregularities in its atomic structure.
The inclusions in polished diamonds are usually invisible when looking at them with naked eye and can be detected only using a loupe or a microscope. This is because polishers aim to achieve stones of best purity without losing substantial weight.
There are internationally recognised categories of diamond purity. They range from loupe clan (flawless) to piqué (included). Internationally recognised diamond laboratories use different terms – for example the HRD (Hoge Raad voor Diamant/Diamond High Council) prefers terms ‘loupe clean’ and ‘piqué’ and the GIA (Gemological Institute of America) uses terms such as ‘flawless’, ‘internally flawless’ or ‘included’.
Diamond value increases with its purity, meaning that the fewer imperfections it has, the more expensive it is. The difference in price between purities of the same size, colour and cut diamonds can vary between 5% and 50% depending on the size, colour and clarity of the diamond. For example, the price difference between 1ct D Flawless and 1 ct D VVS1 is 25%, the difference between 1ct H VS1 and 1 ct H VVS2 is 5%, whereas the difference in price between 1 ct J P1 and 1 ct J SI2 is 32%. These are the price differences at the moment of writing this text and they can fluctuate over time, but this example illustrates how purity can affect diamond value.
A pinpoint is the smallest inclusion visible in the diamond. It is a bright white or black contrasting point. Pinpoints can be observed as single inclusions or in groups, gathered closely together.
A crystal inclusion is larger than a pinpoint and has a definite geometric form and volume. Different minerals with various colours can be present as crystal inclusion in diamond. A type of crystal inclusion is a dark crystal inclusion (also known as ‘grain’) – usually a metal sulphide that existed before the crystallisation of the diamond.
A needle is a long thin crystal inclusion that is usually white or translucent. It looks like a tiny rod at 10x magnification. Such flaws are usually invisible to the naked eye.
A cloud consists of a large group of pinpoints. The number of pinpoints varies from tens to thousands. Clouds can have various shapes, ranging from cubes, through crosses to hexagons. Sometimes, when inclusions are numerous, difficult to distinguish among one another and they are present in a group, they are also called a cloud. In certain cases, if clouds are big enough, they can be visible to the naked eye, then we talk about milky stones. Milky diamonds have a reduced brilliance.
A series of pinpoints, clouds, or crystals that forms in a diamond’s growth place; associated with crystal distortion and twinning planes. It resembles stretch marks. Twinning whisps occur when during the formation process, diamonds stop developing due to poor conditions and resume the growth later (even after thousands of years).
A knot is a crystal inclusion that reaches the polished surface of a diamond. The included crystal can either stand out on the surface or be sunk more deeply in the stone. If knots are on the surface, they can affect diamond durability in the long term.
This inclusion resembles a bird feather. It is a tiny crack inside the diamond, in most cases transparent.
A hole or deep opening within diamond structure. Most cavities are small and visible only under 10x magnifying loupe. They are formed as a result of 2 diamonds colliding or from the tearing of neighbouring shallow cleavages that cause a chip of diamond to pop out of the stone.
Unlike man-made laser drill holes, etch channels are naturally formed. They are formed by intense heat during the diamond’s journey from Earth’s mantle to the surface. Etch channels can take form of hollow tunnels, parallel lines and worm-like channels.
Normally a mechanically caused inclusion provoked by accidental bumps or wear and tear. It is a small opening near the diamond edge, as a tiny piece of gem was chipped off. Chips can be removed by polishing but this can lead to stone’s weight loss.
Inclusion in a form of a sharp blow to the diamond’s surface that extends inside the stone, causing small feather inclusions.
A natural is a part of the original skin of diamond that was intentionally left out when it was cut or polished. It is not treated as a diamond defect, but rather as something that contributes to its uniqueness and beauty. Naturals are quite common in diamonds as often diamond cutters and polishers aim for maximum possible diameter. Naturals are normally found along the girdle of a diamond. Indented natural is a natural that indents slightly into the surface of the diamond.
Laser drill hole
Laser drilling is a technique of improving diamond clarity. A dark inclusion can be bleached with strong acid inserted through a tiny laser-drilled tunnel. This bleached spot along with the channel are considered an inclusion.