Antique Georgian mine or rose cut diamond ring. This is a cluster ring with 23 genuine diamonds. Carat weight is unavailable. This is an early ring and the diamonds are foiled in the back and set into crude bezels with some drops of metal that serve as prongs here and there. The foil is tarnished behind the stones making them look like black diamonds. They are not. 

True to georgian jewelry, the head of the ring is sterling silver, which contributes to the tarnish. The base and the shank are 10k yellow gold. I did test it. Not marked. I expected 9k =, but it passed for 10k and failed for 14k. Likely European. 

Small size at 3.5. Face has a diameter of 18mm.