Best Black Diamond Engagement Rings Once you have decided with the metal then you must consider the stone for your diamond rings. Always remember black diamond engagement rings comes in variety of gemstones such as pearl, sapphire, ruby, topaz, diamond and emerald. But diamond black engagement rings are very popular choice among the people of today's generation. Always remember that it is true that diamonds rings are girl's best friend and are considered as the best gift for engagement. Hence if you are willing to spend lot of fortune and want to impress your lady then best black diamond engagement rings are the best gifts which you can give to your beloved.