(IDEX Online) - An increasing number of colored lab growns are being submitted for grading as natural diamonds, according to GSI.The New York-based lab is warning of a surge in undisclosed brown, yellow and pink stones - from melee to 1.0-cts - in recent months.Most of those detected have been Type IIa with a single nitrogen, all mounted in jewelry rather than loose."Over the past several months, our team has seen a rise in laboratory-grown colored being mixed in with natural-colored diamonds in jewelry" said GSI president Debbie Azar."The challenge arises as most jewelry screening equipment in the market is designed to screen white near-colorless diamonds."Some diamonds are cut to mimic natural stones, and display features associated with natural diamonds in a deliberate attempt to fool grading labs."Severe fractures, pinpoint clouds, and polished-over 'naturals' were observed, including distinct brown grain lines," GSI said."These features closely resemble those found in natural diamonds, potentially passing standard gemological observation."Pic courtesy GSI.