This is a bead made from polished spondalus shell. It is .84" (21.3mm) long, and to give you an idea of how much work was involved to produce this with only primitive hand tools, the holed for stringing are bored through the edge on a diagonal and not through the middle!  This is a genuine artifact of the Mezcala civilization, dating from 1200-600 BC.  That civilization flourished in Western Mexico and ritual cannibalism, blood letting, child sacrifice, and jaguar worship were central.