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