Natural gemstone 35” necklace jewelry

Necklace is in good condition and kept in a clean smoke free home. I tested the stone chips with my presidium II gemstone tester and it jumped around. This means it is a gemstone but not a stone that my device tests. It’s definitely a gemstone but I cannot tell you the exact stone. *** searching through google I found others have this listed as prehnite. *** I do not know the exact stone or value. 35” pale green, clear, and black specks. #gemstone #necklace