Gemstone Certification - Pierre DeRoche PDR 4020 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 undoubtedly 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 brilliant 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 grams.
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 inclusions), SI2, SI3, P1 (Piqué), P2 and P3.
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