This ring is hand fabricated in 14k yellow and white gold, with a 4mm blue sapphire.  The gemstone is bezel set, which is to say there is a smooth rim of white gold around the sapphire, holding it securely in place.  This eliminates the need for traditional prongs, and provides a smooth, very wearable design.  Sapphire is from the corundum family, which is a very hard material and therefor sapphire makes a great everyday wear ring.