This is a larger No. 8 mine Turquoise stone (~30×24) set in a 6mm wide Sterling Silver band. It is a size 10 ring.
I do most of my own lapidary work, sourcing my stones as close to the miner as possible. I create all the sterling silver settings from flat metal or wire.
Hand-crafted art/jewelry are one-of-a-kind pieces and generally are not duplicated exactly. Stones vary, measurements vary. I can collaborate with you if you would like to have a piece made for you or for someone else. Sterling silver may be polished with any number of good silver cleaner/polish products. Natural stones are fragile and may break if dropped, heated directly, stepped on, etc. Care should be taken.