How to Choose a Black Diamond

Black diamonds have had an inconsistent market history. Profuse black occlusions, or natural cracks that are refracted internally, give the stone its opaque look. They also make it difficult to facet. For ages, black diamonds were relegated to industrial grade and used in constructing drill bits. A recent wave of popularity from buyers has returned them to the jewelry store. Learn what to look for and choose a black diamond.

Instructions

Difficulty: Moderate

Learn the Make-Up of Black Diamonds

1. Compare black diamonds' origins to colorless and fancy diamonds. All are crystallized carbon, but black diamonds' color comes from intrinsic flaws, whereas the others rely on the absence of flaws for their light-reflecting properties.
2. Acquaint yourself with the more common but lower-quality "carbonados," or heavily occluded black diamonds. These are usually so intensely fractured that they may be polished but not faceted.
3. Get to know the second type of black diamond, the "true black." Their color comes largely from infused graphite shards, rather than just occlusions, so they are somewhat more easily polished and faceted.

Learn the Hallmarks of Finished Black Diamonds

4. Choose to view true blacks, rather than carbonados. These will have longer lives in jewelry settings since they are not as prone to crumbling along fault lines.
5. Examine black diamonds by eye for color. The more consistently opaque the stone is, the better. Pass on diamonds that have transparent spots.
6. Evaluate diamonds under a jeweler's magnifier and strong light for clarity. You will likely find occlusions, but the fewer the better.
7. Assess the stones' finish. Rate the degree of polish and attractiveness of any facet or bevel cut. You should not be able to see any spidery cracks on the surface.
8. Choose the best stones to compare against one another. The best true black diamonds should resemble highly polished black onyx.

Tips & Warnings

• Real black diamonds do not have "sparkle." Brilliance comes from reflected light, and black diamonds absorb light instead.
• In addition to being nearly impossible to facet due to occlusions, black diamonds are difficult to polish. If you find a stone with a lustrous polish, it will probably command a relatively higher price.
• While demand for black diamonds has increased, it still represents only a fraction of diamond sales. Therefore, you can find quality black diamonds at reasonable prices.
• While neutron irradiation is not legal in the U.S., it is used to treat black diamonds for color in other countries. Check your laboratory documentation to see that a stone has been tested for residual radiation.