PRESIDIUM Synthetic Diamond Screener II Bedienungsanleitung Seite 6

Each instrument is tested on the ASSURE Core Sample, a highly
contaminated sample made up of 1,000 mined diamonds and 200
laboratory-grown diamonds including very challenging laboratory-
grown diamonds, some of which are not yet available in the market.
Types of diamonds
Diamonds can be classified into two Types.
Typically, Type I diamonds contain nitrogen atoms as the main
impurity and these diamonds make up almost 98% of all mined
diamonds. The usual color of Type I diamond is colorless, brown,
yellow or orange but can also be virtually any color other than blue.
Type II diamonds, however, contain few or undetectable nitrogen
atoms and they make up the remaining 2% of mined diamonds.
Within the Type II category of diamonds, they can be further classified
as Type IIa and Type IIb. Type IIa diamonds are usually the purest of
color ranging from colorless to near colorless, although they can also
be of yellow, brown, orange, pink, red or purple colour. Type IIb are
typically not colorless and are usually blue, brown or gray and contain
boron atoms as well.
Currently, known laboratory-grown colorless diamonds are generally
Type IIa diamonds i.e. colorless diamonds without any detectable
presence of nitrogen atoms. Type IIa colorless laboratory-grown
diamonds can be grown either using chemical vapor deposition (CVD)
synthesis or High Pressure High Temperature (HPHT) synthesis, or
can be HPHT-treated CVD diamond.
This device helps to identify the Type IIa colorless diamond, which
may be a laboratory-grown diamond, but does not distinguish between
the various processes through which the laboratory-grown diamond
may be grown or treated.
When subjected to deep UV irradiation, Type Ia and Type IIa
diamonds absorb different amounts of UV light and this difference
in the light absorption is significant enough to aid in differentiating
between Type Ia and Type IIa colorless diamonds.
The SDS II is developed and designed based on this principle. Type
IIa diamonds allow more deep UV light to pass through and thus its
UV light absorption ability is lower.
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Diamond Grading ABC The Manual. 9th edition, 2007, Verena Pagel-Theisen G.G.
F.G.A
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