Ross-Simons - 1.00 Carat Black Diamond Solitaire Ring Round Cut in 14kt White Gold. Size 10. Our classic black diamond solitaire ring is sure to bring a smile to her face. Beautifully set with the dark, dramatic sparkle of a 1.00 carat round brilliant-cut black diamond in a 14kt white gold setting. Black diamond solitaire ring. Diamond birthstones are the perfect gift for April birthdays.