Considerable scientific work has been done on
this topic, although citing every reference is beyond
the scope of this article (see, e.g., Robertson et al.,
1934, 1936; and Kaiser and Bond, 1959). Brief gemological
discussions of diamond types appeared in
Shigley et al. (1986), Fritsch and Scarratt (1992), and
Smith et al. (2000), and more-detailed descriptions
were given in Wilks and Wilks (1991) and Collins
(2001). Nevertheless, repeated inquiries received at
GIA indicate that many practicing gemologists do
not have a clear understanding of the basics of diamond
type. This article offers a readily accessible,
gemology-specific guide to diamond type and related trace-element impurities, including how impurities
are measured, why type is important, and how type
can be determined using simple gemological tools.
With this foundation, it then explains the application
of diamond type concepts to the detection of
diamond color treatments and synthetic diamonds.