These are simply gorgeous black pearl earrings set in 18K white gold studs. They are 9.5 mm in diameter or just over 5/16”. At some point, one of the earrings backs was replaced with a 925 sterling silver one, so there is one 18K white gold back and one sterling silver back currently. The posts are 18K white gold (tested). They are slightly different in color, with one showing more of a purple glow, while the other has some purple and blue/green undertones. With one on each ear, the difference would be unnoticeable. The luster is excellent and I do not see any chips or scratches. Great staple piece for any wardrobe!