In the name of God and God's blessing. Three sterling silver rings for sale. 1 Dark blue emerald sapphire corundum stone from Fayendra. 2 Agate black stone. 3 Agate red stone. Sterling silver, an alloy of silver containing 92.5% by mass silver and 7.5% by mass other metals, usually copper. Sterling silver has a minimum fineness of 925, which is the number shown inside the rings