A lovely natural green beach stone is prong set on cupped sea urchin disk.   The band is a flat 1/4" wide lightly textured strip and is very comfortable.  I collected this stone on a Pacific Northwest beach.   Size 7.5
 
Details:
Stone green beach stone (3/4" x 3/4")
Sea urchin disk: (1" x 1")
Band: Sterling silver
Recycled sterling silver
Finish: oxidized
Size: 7.5