Sea glass is any man made glass that's been in saltwater for decades. The combination of agitation and the slow chemical etching caused by salt will transform what was a piece of grangma's broken candy dish with sharp edges to become frosty and smooth with rounded edges. 

are then persistently tumbled and ground until the sharp edges are smoothed and rounded. In this process, the glass loses its slick surface but gains a frosted appearance over many years.

Naturally produced sea glass originates as pieces of glass from broken bottles, broken tableware, or even shipwrecks,