Explosive mineral formations encountered by the Enterprise crew on the planet Gamma Trianguli VI contained uraninite, hornblende and quartz. It was extremely fragile, had good cleavage, and was unstable. (TOS: "The Apple")
- Spock notes in this episode that these minerals could be a find of some importance, given that it could be a considerable power source in large quantities. This statement leads directly to speculation that the minerals might be a power-source for Vaal, since nothing else available on the planet would seem to have enough energy content to satisfy the appetite of a machine such as it. On the other hand, based on the explosions seen in the episode, it is doubtful that the rock contains much more potential energy than petroleum.