Vintage sterling silver Native American ring Southwestern design size 7

Vintage sterling silver ring. The stone is either malachite or green turquoise. This is a large bold piece. The ring is not hallmarked sterling but does acid test as sterling. It has an artist signature carved on the band, artist unknown. The silver has darkened with age, if you do not like this look, the ring can be polished. It measures a size 7 on a mandrel.