You may have found it in the back of a drawer somewhere - a plastic bag with a green stone inside, probably opaque or nearly so, labelled "Tamiz Emerald", possibly accompanied by a certificate of authenticity from "GCI" in New York.
These stones were sent out as prizes in a dodgy mail order sweepstakes during the 1980's. Technically, they're emeralds, but so poorly cut and full of inclusions as to be practically worthless.