Gemstone Moon of Regol Genaralon

Located in the Regol Genaralon, the Gemstone Moon was so called because of its superb crystalline structures — each completely unique. It was not, however, the crystalline structures that attracted a team of scientific researchers to the moon, where they erected a pre-fabricated base. Instead the base was built around a Grey Hole. The Grey Hole became very dangerous. The Eleventh Doctor negotiated the safe release of the scientists in exchange for suspension of the research work. (COMIC: The Grey Hole)