Diamond Clarity
Clarity
Clarity is possibly the most important of the factors affecting the quality and price of any diamond. Diamonds
of all colours can be vary attractive. Diamonds of all different cuts look good, and not many diamonds are
very badly proportioned.
Extremes of clarity can produce a brilliant magnificent diamond, or a dead, dull, and lifeless stone. Clarity is
also sometimes called purity. The fact that clarity is also sometimes called quality shows the importance of
this factor.
Clarity literally means "clearness" rather than lack of inclusions, and refers to the diamond's ability to allow
the free passage of light without obstruction or absorption. Any inclusions, cleavages, cracks, or other
natural features inside or defects on the surface will stop light from passing through the stone.
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.
Grading Standards
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.
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