Black diamonds are amongst the most popular of the colored diamonds. They have gained in popularity over the last few years. The trend is that they are used in engagement rings and the demand for these beautiful gems has increased dramatically.
There are several types of black diamonds, albeit not exactly the same. There are natural black diamonds (from the ground), man-made black diamonds and there are treated black diamonds. All are real but there is a vast difference between the different types of black diamonds and if you plan on buying one, you should know that there is also a significant difference in value.
Black diamonds (in their natural form), have not remained under the earth's surface as long as normal diamonds would have. They are also more porous than normal diamonds, however, still an extremely strong stone.
Natural Black Diamonds are actually quite different than other colored diamonds. They are an impure form of polycrystalline diamond consisting of diamond, graphite, and amorphous carbon. While regular natural colored diamonds receive their color from the impurities that are are present in the ground during the formation process (for example boron causes blue diamonds), black diamonds are similar to white diamonds that have an extremely high amount of inclusions, clusters of graphite inside of them to the point that they simply appear black.
Treated black diamonds are regular white diamonds that are usually of extremely low value due to the high amount of inclusions in them. In a way, a more suitable name for these diamonds is colorless treated black diamonds or simply black colored diamonds. Since for the creation of this type of black diamonds, extremely low quality white diamonds with little value are used, these are the cheapest type of black diamonds.
Man made, or lab grown, synthetic are not diamonds in the normal sense of the word. These are basically all more or less the same and obviously rarity with these stones is minimal, hereby devaluing the stones.