ringstone

noun

1. A carved, contoured, donut-shaped stone object in early Indian art.
2. A gemstone for use in an ornamental ring.

   “This involves some of the intaglios or incised ringstones of the Roman soldiers, with a variety of designs from the head of Jupiter on something the size of your forefinger nail, to the multi-tasking dancing girl, who is certainly swinging her skirts but also playing the pipes at the same time and on a semi-precious cornelian stone of a beautiful blue.”