Black diamonds were a very rare form of diamonds. Their colour came from the presence of tiny mineral inclusions. Black diamonds contained iron oxide mineral magnitude and hematite. Sometimes they occurred in such a high proportion that they were magnetic. (AUDIO: The Time Capsule)
In 1898 the Eighth Doctor and Lucie Miller became embroiled in an attempt to steal an infamous Black Diamond. (AUDIO: Grand Theft Cosmos)
The Black Diamond of Earnfield was a black diamond that was shown at an exhibit of the Natural History Museum in 2009. Originally it had been a part of a Persopolisian control console, which could be used to start a Persopolisian space ship. It was stolen by Luke Smith and fell into a garbage compactor where it was destroyed. Mr Smith later made a duplicate of the diamond which Sarah Jane gave back to the Natural History Museum. (AUDIO: The Time Capsule)