The Swiss Gemmological Institute (SSEF) has issued a trade alert over a growing fraud in the emerald market involving gemstones that are re-treated after laboratory testing and sold with reports that no longer reflect their true condition.
SSEF said some emeralds are being stripped of fillers such as oil, wax or resin before being submitted for testing. As a result, laboratories may issue reports stating “no” or “minor” clarity modification. The stones are then re-filled after certification and offered for sale with the original report, creating a misleading impression for buyers.
Clarity enhancement is a widely accepted practice in emeralds, but under international LMHC guidelines, any filler and the extent of treatment must be disclosed because they significantly influence value.
The institute noted that rising demand for minimally treated or untreated emeralds has fuelled the practice. Buyers are increasingly paying premiums for stones showing little or no clarity enhancement.
SSEF stressed that laboratory reports reflect a gemstone’s condition only at the time of examination. Any subsequent cleaning, filling or alteration can render the report outdated and potentially misleading.
To protect the trade, SSEF recommends re-testing fissured emeralds before purchase, particularly when reports are not recent, and exercising caution when a visually clean stone is accompanied by a report stating no clarity modification.
The institute also warned that the same risks apply to other fissure-bearing gemstones, including rubies, and urged greater vigilance across the coloured gemstone trade.