Gemstone Certification - Pierre DeRoche Chrono Penta PDR 4012 Mode D'emploi

Gemstone Certification

There are 4 main categories of precious stones: diamonds, emeralds, rubies
and sapphires.
The one most sought after in the field of watchmaking and jewellery is undoub-
tedly the diamond. The factors determining the quality and thus the value of
this gemstone can be summed up in the "4Cs": Cut, Carat, Clarity and Colour.
Cut
There are 9 major forms of diamond cut: Brilliant, Oval, Radiant, Marquise,
Heart, Emerald, Pear, Princess and Triangle. The most frequent is the brilli-
ant cut which comprises 56 facets + the table, meaning 57 facets in all.
Carat
The metric carat is a unit of weight specific to precious stones. It bears no
relation to the unit of the same name used for gold alloys. The metric carat
corresponds to one fifth of a gram, meaning 0.2 gram.
Clarity
The most widely used scale of clarity is based on an examination of the precious
stone under a 10-power magnification: FL (Flawless, meaning the absence
of any internal or external flaws), IF (Internally flawless), VVS1 (Very very
small inclusions), VVS2, VS1 (Very small inclusions), VS2, SI1 (Small inclu-
sions), SI2, SI3, P1 (Piqué), P2 and P3.
Colour
Several grading scales are used, some of which are local, and they are linked
between themselves by correlation tables. Among the most widely known is the
"GIA" (Gemmological Institute of America) scale ranging by decreasing quality
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