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.