gems, lapis lazuli, Afghanistan, oiled lapis lazuli, gem treatments, oiling

An importer of fine lapis lazuli beads from Afghanistan noticed a variation in luster among the beads and suspected that some had been oiled to enhance their appearance. After confirming the beads as genuine lapis lazuli, the New York laboratory used a thermal reaction tester and magnification to investigate the presence of oil or paraffin. All beads exhibited the typical reaction of oil being drawn to the surface by the heated probe, with some showing heavy oil concentrations in drill holes and surface cracks. The lack of whitening upon cooling indicated the presence of oil rather than paraffin. Microscopic examination and acetone testing revealed no evidence of blue dye. While oil or paraffin treatments have historically been used to “set” dyes in stones like jade, lapis lazuli, and amazonite, the beads in question were not dyed, and the reason for oiling alone remains unclear—possibly done to mask a poor polish.