Feature Gems & Gemology, Winter 1983, Vol. 19, No. 4

Cobalt Glass as a Lapis Lazuli Imitation

A necklace of round beads offered as "blue quartz from India" was analyzed by gemological and additional advanced techniques. The violet-blue ornamental material, which resembled fine-quality lapis lazuli, turned out to be a nontransparent cobalt glass, unlike any glass observed before as a gem substitute. The characteristic color irregularities of lapis (white in blue) had been imitated by white crystallites of low-cristobalite included in the deep blue glass.