Figure 1. Natural sapphires,
such as these 45
princess cuts from
Madagascar, come in a
broad range of colors.
Nevertheless, the high
demand for fine ruby
and sapphire has led to
a wide variety of treatments,
of which heating
to improve color
and/or clarity is perhaps
the most common.
These sapphires
have a total weight of
23.08 ct. Courtesy of
Pala International,
Fallbrook, California;
photo © Jeff Scovil