Vintage prehnite stone from the Lake Superior region sometime in the 1950s most likely. It is translucent, a beautiful shade of spring green that almost looks blueish at times. Noting – I am pretty sure it is prehnite, but there is an outside chance it is something called datolite. This is a natural stone with natural internal and surface flaws but in good condition with a nice polish.
It’s paired with as silver chain necklace (.925 silver / silver-on-copper) about 20 inches long.