925 sterling silver pendant with natural diamond and blue gemstone

Stunning sterling silver pendant with deep blue gemstone and one small natural Earth mined diamond. In excellent condition. Stamped 925 and also has a makers mark MHJ (Michael Hill Jewelry). 1.6 cm long. The diamond is on the left side of the pendant, securely prong set, and was professionally tested. Not sure what the blue stone is. It tested as a real gemstone and looks like a Tanzanite, or a Sapphire. Not sure how to tell.