Navajo sterling silver ring. Sterling and artist stamped

Really cool Navajo sterling silver ring. Not exactly sure what the stone is, I originally thought it was mother of pearl, but it has more of a lilac hue to it. Sterling silver and artist stamped Size 6 Excellent used condition- this belonged to my mother, she was a huge collector of Southwest jewelry. It has likely only been worn a few times. Band is slightly misshapen - see photo