International Gemological Institute (IGI) is learnt to go beyond its conventional corporate norms and offer batch testing to detect all surface-coated tanzanite. IGI corporate rules do not permit grading of diffusion treated and coated stones, but the lab will batch-test for surface coatings of cobalt, to determine a “quality assurance document”, clarifying if the stone has undergone any surface coating treatments.
The lab has identified that a minimum of 10 stones, regardless of individual weight be batch-tested at one time, which will cost $50.00 or $5.00/stone. If less than 10 stones are tested, the cost is unaltered. The turnaround time for IGI’s tanzanite batch testing is 24 to 72 hours. The lab is a pioneer in tanzanite-specific grading system.