This material is often confused for Petoskey stone the difference this material has a much tighter more defined pattern and comes in different colors.  Both of these rings are designed on a saddle band (think English riding saddle smooth and wide on top and narrow underneath).  A) would be perfect for middle or forefinger and measures    2"long x 1 3/4"wide.  B) 1 5/8"long x 1"wide.