Out of the wide range of black gemstones available on the jewelry market, black diamonds and black sapphires are two of the most popular. Both are exceptionally hard and well-suited to everyday wear, richly-colored, and can originate naturally or as a result of color treatment. Black diamonds are a little bit more prone to breaking than sapphires, but they do carry the prestige of a real diamond. Black sapphires, on the other hand, were considered inferior for a very long time and are still catching up to the black diamond jewelry trend. This means they can be found much more affordably than natural black diamonds, but will have almost no resale value. For a black stone engagement ring, both of these gemstones are a very good choice.