I collect my Beachstones personally  every year from the beaches of New England in the U.S.   I do not alter my collection in any way other than drilling the holes for the handmade sterling silver bails. So their shapes and other attributes are made by the salt, sand and sea. Once you start really looking closely at the pebbles on the beach you start to notice some shapes and colors are difficult to find. Especially the very symmetrical, the very smooth and my personal fav...the very smooth and black. 
I encourage you to take a closer look at beachstones you see on the shore or on a walk through the woods. Touch them. Look for symmetry. Compare the colors. It's an experience that puts things into perspective sometimes. 
Thanks for stopping by my little shop. 
Christine