NEW with tag Tanzanite CZ sterling silver pendant necklace

This necklace was purchased from an estate and is brand new , never worn and still has its original tag in place.  This tests between cubic zirconia and tanzanite. I'm sure it's tanzanite but could be either but I’m pricing as cubic zirconia just to be safe. Set in rhodium plated over sterling silver. Chain measures 20 inches. 925 STS Reasonable offers considered