GIA Lab Encounters 28 Carat HPHT Diamond

The Gemological Institute of America’s New York lab recently
received one of the largest HPHT stones it has ever seen for grading—a 28.65 ct.
brownish yellowish orange emerald-cut diamond, it announced in its Gems & Gemology e-brief.

The stone was submitted without disclosure of its origin,
GIA noted. GIA recently reported an increase in undisclosed HPHT stones at its lab.

GIA says that the 28-carater’s starting material probably
had a light yellow or brown body color, but the HPHT treatment produced a
strong yellowish orange hue with a brownish modifier.