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|Diamonds - The 4 C's - Clarity|
What Are Inclusions?
Geologically, an inclusion is "a solid fragment, liquid globule, or pocket of gas enclosed in a mineral or rock."
In gemmology, this definition is usually extended to include any other feature of the gemstone which impedes the free passage of light through the stone. This includes changes in crystal growth direction (e.g. twinning), and external features, such as fissures which run from the surface into the stone, naats , trigons, and zones of colour absorption (e.g. the very common colour banding seen in sapphire).
Are All Inclusions Visible?
No, not all inclusions are visible either with the naked eye, or under the standard 10 times magnification used by gemmologists. Many consumers believe that inclusions are things which are visible to the naked eye, and that if no inclusions can be seen, then the stone is perfect. Some stones contain many areas of "twinning", where the growth direction of the crystal has changed during its formation, and these areas can absorb or refract light in such a manner as to reduce the brilliance of the stone. Other stones contain large numbers of small inclusions, some visible under 10x magnification, others not, because they are too small. These clouds of microscopic inclusions can reduce the passage of light through a stone so severely that the stone looks "dead", with no brilliance or fire whatsoever. Such stones usually have a slightly cloudy look to the naked eye.
What Are Carbon Spots?
A common belief, shared by some jewellery shop staff, is that any black marks visible in diamonds are composed of carbon. Diamonds are composed purely of carbon. While it is possible that some inclusions may be of graphite, the commonest form of carbon, or amorphous carbon, such inclusions are quite rare. Dark inclusions in diamond can include other diamonds, olivine, garnet, diopside, pyrrhotite, pentlandite, pyrite, ilmenite, rutile, silica, bronzite, spinel, serpentine, biotite, phlogopite, chlorite, calcite, haematite, goethite, and iron oxides.
In recent decades, the GIA, Gemmological Institute of America, has influenced other gemstone grading bodies, such as CIBJO, throughout the world, and most countries now use the same standards as the GIA for diamond clarity, so that the GIA scale has become virtually an international standard. There still remain vast differences between commercial grading and laboratory grading.
De Beers supply leaflets and showcards for diamond clarity grading, but as their aim is undoubtedly to increase demand for higher quality diamonds at higher prices, the De Beers charts contain some distortion. They typically graphically represent the higher grade bands as wider than the lower grades, whereas in reality it should be the other way round, and the grades below P3 are not even mentioned, as though they do not exist.
We present the following table of diamond clarity grades:-
|GIA||UK / CIBJO||Description||Clarity||Our Comments|
|IF||Loupe Clean||Internally Flawless||Internally Flawless|
|VVS1||VVS1||Very Very Small Inclusions||No Visible Inclusions|
|VVS2||VVS2||Very Very Small Inclusions||No Visible Inclusions|
|VS1||VS1||Very Small Inclusions||No Visible Inclusions|
|VS2||VS2||Very Small Inclusions||No Visible Inclusions|
|SI1||SI1||Small Inclusions||No Visible Inclusions|
|SI2||SI2||Small Inclusions||No Visible Inclusions|
|I1||P1 - Piqué1||SI3||Barely Visible Inclusions|
|I1||P1 - Piqué1||First Piqué||Barely Visible Inclusions|
|I2||P2 - Piqué2||Second Piqué||Easily Visible Inclusions|
|I3||P3 - Piqué3||Third Piqué||Very Easily Visible Inclusions|
|Heavily Spotted||Very Heavily Included|
Comments On Our Chart
The clarity bands from IF to VS could be described as unnecessarily good, or luxury grades. In these grades, diamonds suffer no noticeable loss of brilliance through lack of clarity. Any diamond in these grades should be very bright and sparkly. Inclusions are difficult to see when using a 10x magnification in good light, and are not visible to the naked eye.
In SI1 and SI2, the same comments apply, except that the inclusions are fairly easy to see under 10x magnification, and there may be some, barely discernable lack of brilliance.
SI3 is a relatively recently invented grade. It is not recognised by the GIA or many other laboratories, but is in fairly common commercial use, and is intended to imply that the diamond is better than P1, but logically, it means that the diamond is below SI2, and therefore should apply to stones which are almost SI2. We include it in our table because it does have practical use.
Diamonds which fall into the Piqué bracket have inclusions which are visible to the naked eye. In our opinion, the dividing line between SI2 and P1 is a very important one. The word Piqué is French, and means "pricked".
In P1 stones the inclusions should be difficult to see, or very minor.
P2 stones would have inclusions which were more easily seen. P3 stones would have very easily visible inclusion.
All stones graded P1 to P3 should still be bright and attractive.
Laboratories are not often asked to grade diamonds lower than P3, so they do not have grades below P3. There are many attractive and valuable diamonds which fall into lower grades, and the traditional terms for these are shown. Diamonds described as "Spotted" or "Heavily Spotted" can be expected to have more, or larger, inclusions than those graded P3, but will still retain some brilliance, and be reasonably attractive.
Diamonds falling into the "Rejection" or "Near Gem" category will have very limited, if any, brilliance, and could be considered as "fun" diamonds. They have little commercial value, and often sell for less than their cutting cost.
The blank "Clarity" column is reserved for a graphical representation which will follow shortly.
Diamond 4C's Tour - Next Stop - Carat Weight
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