Diamond flaws

Diamonds flaws are common. Few diamonds are perfect; most of them have some inclusion or imperfection. These inclusions are also known as flaws and exist in various forms, exterior and interior. Inclusions are also classified in the manner in which they were formed. For example, syngenetic diamond inclusions are those inclusions which were formed while a diamond was being made, while epigenetic inclusions were formed after a diamond was made.

Flaws

The presence or absence of flaws or inclusions in a diamond is usually decided by examining the stone carefully with a lens having the standard magnifications of 10x. No other magnification should be taken as authoritative. Stones which show no apparent flaws or inclusions under this magnification are regarded as flawless. The term for a scarcely perceptible inclusion is "VVS" for "very very slight (or small)" – which is sometimes offered as flawless. Slightly larger flaws or groups of very thin inclusions are termed "VS" ("very slight"). Larger flaws or inclusions are termed as "SI" (or slightly included). Even larger flaws are termed as "1st pique". Slightly larger flaws classify the stone as "2nd pique" and so on.

Any flaws which are visible with the naked eye would be sufficient to scale the price down considerably.

External flaws

Blemishes

These diamond flaws are present on the surface of a stone and can occur naturally. However, these are more likely to be caused by the external environment when a diamond was being cut and polished.

Scratches

These are fine lines found on the surface of the diamond. They may have been present naturally or caused when a diamond was cut. While minor scratches can be removed through proper polishing, deep scratches can rarely be removed by treating the diamond.

Extra facets

These are usually cut to remove blemishes or certain close to surface inclusions on diamonds. At times these extra facets are also cut to enhance the brilliance of the diamond. These do not usually affect the clarity grade of a diamond.

Fracture

A breakage in diamonds that is not parallel to the cleavage plane is referred to as a fracture. Fractures are usually irregular in shape, making a diamond look chipped. The practice of fracture filling is commonly employed to improve the diamond clarity of such diamonds.

Fingerprints

Fingerprint inclusions in the shape of fingerprints can sometimes be found in diamonds. However, such inclusions are rare in diamonds as compared to other stones, such as rubies. Such inclusions are usually formed during fluid assisted partial healing of fractures already present in stones. For this to take place in diamonds, high temperatures and pressure (HTHP) are required, which is unusual. Few such inclusions have been reported in natural blue and colorless diamonds. While this could indicate that diamonds have been HTHP treated, giving the required temperatures for fingerprint inclusions, such is not always the case. The earth may also cause geologically high temperatures, leading to the formation of fingerprint inclusions.

Pits

Small holes may be present on the surface of a diamond. These pits are usually not visible to the naked eye. However, pits present on the table facet of a diamond are usually visible and reduce the clarity of a diamond.

Nicks

Diamonds are also chipped at places causing the appearance of nicks. This is often repaired by adding extra facets. However, too many facets reduce the brilliance of a diamond and are to be avoided.

Naturals

This refers to the original surface of the diamond, which has been left alone and unpolished. Naturals are usually left on or near the girdle of the diamond. While these are considered as blemishes, the presence of naturals is a sign of good cutting practice, where the cutter has managed to retain as much of the original weight as possible. Indented naturals are also seen to exist on some stones, where the portion of the natural is seen to dip inside slightly from the diameter of the stone. Here the cutter usually leaves the indented natural either at the girdle or pavilion of the stone, in order to keep it less noticeable. In such positions, the natural is not visible even with a loupe. Indents can be removed if the cutter polishes out more roughly. However, this would result in a drop of the diamond's weight by up to 25%.

Carbons

Diamonds are made from carbon, usually graphite. Nevertheless, while a diamond is being formed, it may not totally crystallize, leading to the presence of small dots of black carbon. These black spots have been classified to be those of graphite, pyrrhotite and pentlandite. These surface flaws resemble a small black dot and may affect the clarity of the stone depending on the size of the imperfection. The occurrence of this kind of flaw is less common in diamonds compared to pinpoint inclusions. Carbons are usually seen in white or blue-white stones. Carbons are not commonly found in diamonds of poorer colors. Within the trade, these are called "carbon spots" and may be cleavage cracks which have developed through uneven heating or a blow. Cleavage cracks often appear to be dark or black in normal lighting conditions because of light reflection.

Chips

The breaking off of a small piece of diamond towards the surface is usually referred to as chipping. The term may be confused with "diamond chips", which refer to very small pieces of diamonds. These are usually caused due to minor impact from the environment. Downward impact caused when a stone is being set or is being worn, can cause chips on the culet of the diamond. As these are commonly caused when a diamond is worn, it is suggested that while diamonds are being set, a little space be left between the base of the diamond and the head of the prongs of the ring. This space acts as a cushion protecting the diamond from possible chipping when it falls. However, chips are easy to remove by treating the diamond.

Internal flaws

Every natural diamond crystal contains impurities and typical intrinsic or "self-defects": vacancies, dislocations, and interstitial atoms. The most common impurity in diamond is nitrogen, which can comprise up to 1% of a diamond by mass. Nitrogen as a diamond impurity was first identified in 1959 by Kaiser and Bond of Bell Telephone.[1]

Crystal/mineral inclusions

An inclusion is visible in near the center of an uncut diamond

Some diamonds show the presence of small crystals, minerals or other diamonds. These are classified in different categories depending on the size and structure of the inclusion. While many such inclusions are small and invisible to the naked eye, some diamonds may have large inclusions able to be seen with the naked eye, and can affect a diamond's clarity and life. Some crystals resemble a diamond inside a diamond and may also add to the appearance of the stone. These take on shapes of bubbles, needles or grains and are classified as below.

Pinpoint inclusions

As the name implies, these inclusions are minute crystals usually white in color present inside the diamond. These resemble a small point of light and are, by far, the most common of all flaws found in diamonds. Most pinpoint inclusions do not affect the clarity of a diamond and are not visible to the naked eye and are usually not indicated on the plotting diagrams of diamond reports. Comments such as "pinpoints not shown" may be listed in the comments section.

Needles

Diamond crystals in a diamond can also be present in the form of long and thin needles. These may not be visible to the naked eye, unless the needle inclusion is of a noticeable color or has a noticeable presence. Some needle inclusions are also known to give diamonds a special look.

Cloud

The presence of three or more pinpoint inclusions close together can create an area of haze, or a cloud, in the diamond. While the occurrence of a small cloud is not visible to the naked eye, presence of many pinpoints covering a large area can affect the clarity of the diamond. These are usually indicated on grading reports in the form of tiny red dots close together or as circles and other formations.

Knots

When diamond crystals extend to the surface of the diamond, they are referred to as knots. These can be viewed under proper lighting conditions with a diamond loupe. Certain knot formations may also cause raised areas on particular facets of the diamond. The presence of knots may affect both the clarity and durability of the diamond and are best avoided.

Grain lines

Crystal inclusions in diamonds can also occur in the form of lines known as grain lines. These are usually formed due to improper crystallization of the diamond, when it was being formed. Grain lines can also be caused due to improper polishing of the diamond. Even skilled diamond cutters may come across diamonds with variations in hardness when a facet is polished. This can cause microscopic lines across the facet. These grains are usually difficult to remove without excessive weight loss. Grain lines are commonly seen in pink fancy diamonds. A saturation of grain lines on pink stones can also make them look red.

Feathers

These are cracks in the stone that resemble the design of feathers. The presence of feathers in a diamond usually does not affect the life of the stone unless and until the feather runs through a major length of the stone or shows major stress points where it can break. If the cracks reach the surface or have deep fissures, the durability of the stone may be reduced with the possibility of the stone breaking with age.

Intergrowths

Twinning wisps or intergrowths may also be seen in diamonds. These formations are usually inclusions in diamonds that have twisted together during the time of diamond formation. Thus, various inclusions such as pinpoints, needles or feathers may form together, creating a white strip inside the diamond. Surface graining may also be seen in some cases. Such intergrowths are more commonly seen in fancy cut diamonds and are extremely rare in ideal cut diamonds.

Cleavage

These are cracks in a diamond that occur in a straight line and are parallel to one of the diamond's crystallographic planes. Cleavages are usually caused by deep internal strain in a diamond and could also have been caused by a strong blow to the diamond. It usually shows no feathers and has a great chance of causing the stone to split, especially if placed in the high pressure grip of prongs in rings. Stones with cleavage must be chosen carefully and avoided as often as possible.

Etch channel

Etch channels are created during a diamond's formation process deep in the Earth. In the journey of the rough diamond to the Earth's surface, the contact with high-temperature fluids etches into the diamond's crystalline structure which often leave parallel lines or irregularly shaped tunnel-like structures.[2]

Bearding

Also known as girdle fencing or "dig marks", this is caused around the diamond's girdle as the diamond is cut or bruted. These fine lines usually resemble a strand of hair and do not present a problem. However, extensive bearding can lessen the brightness of the diamond. It is suitable that such diamonds be cut or polished again to improve luster.

Diamond flaws are not always negative features. In fact, these flaws often lend a diamond its distinctive beauty and make a stone look unique.

See also

References

  1. ↑ Kaiser, W. and Bond, W. L. (1959) Nitrogen, a major impurity in common type I diamond Phys. Rev. 115, 875-863.
  2. ↑ http://onlinediamondbuyingguide.com Etch Channels in Diamonds Retrieved Jan 9, 2013

External links

Wikimedia Commons has media related to Diamond.
This article is issued from Wikipedia - version of the Saturday, April 02, 2016. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.