3/4" diameter sterling silver "pebble" - Sizes 5, 6, 7, 8, 9, 10 

It's that perfectly rounded pebble you find and keep. Your "good luck" pebble - soothing to feel and calming to hold. As a ring, it radiates quiet power as a minimalist modern statement formed by nature's forces.  

Still waters run deep, as they say.