Swiss blue topaz/white topaz or iolite/white topaz set in 18ct gold plated sterling silver.
The rings are available in a size 6/M or size 7/N but are adjustable so will fit a slightly larger finger as well.
The stones in these rings are stunning, they are 1.75ct each (7mm x 9mm). The rings are jeweller made.
Seen here with the Azure pebble necklace.