Necklace, faceted crystal tennis 16” + 1” dangle

Necklace is in good condition and kept in a clean smoke free home. It looks vintage but age is unknown and appears to be faceted crystals in faux diamond clear and black. Fold over clasp, 16” plus an additional inch where it dangles a larger black and a larger clear crystal. Pretty necklace looks expensive. I tested the crystals with my gemstone tester and they are not gemstones. No markings, brand unknown.