Black diamonds are a popular alternative to white or clear diamonds in engagement rings because of their dramatic color. Many jewelers will pair black and white diamonds together in engagement rings for an even greater contrast. The diamonds in black diamond engagement rings are real, and the most expensive black diamond engagement rings are made with high-quality, naturally occurring black diamonds.
Naturally occurring black diamonds are very rare and expensive, so many of the black diamonds that are set into engagement rings are clear diamonds treated at high temperatures. This process turns white diamonds a dark green color that appears black in natural light.
Once the color changes, it is harder to spot flaws in the diamonds, so lower-quality white diamonds are used for this process. As a result, engagement rings made with black diamonds are often much less expensive than those made with clear or white diamonds.