From: Elementary, ep. 4.24
Object: a beautiful old ring with a large blue stone set at its center
Reference: well, duh, obviously this has to be The Blue Carbuncle, though in this ep it isn’t actually named as such (though we hear the name of the Duchess of Morcar in connection with it, which is in the original). Here, it’s not a loose stone but a ring, not hidden in a goose but in Sherlock’s fireplace, and is an heirloom of Sherlock’s mother’s, which Morland Holmes is looking for (Sherlock thinks) to use as a bribe. As in Doyle, however, Sherlock does not give it up, but keeps it. No, really, he keeps it in the canon too–read it. He keeps the black pearl of the Borgias and the Mazarin stone, too, you know.