Shungite and white topaz necklace in sterling silver

This necklace is in excellent pre owned condition showing little to no signs of wear.  Black stones test as shungite , white accent stones test as topaz. Prong set in either platinum or rhodium plated over sterling silver. Measures 18-20 inches with chain extension. Measurement doesn’t include teardrop stone hanging off the middle lowest point. Spring ring clasp. 925 STS