Dilithium crystal
In the Star Trek fictional universe, dilithium is an invented material which serves as a controlling agent in the faster-than-light warp drive. In the original series, dilithium crystals were rare and could not be replicated, making the search for them a recurring plot element. According to a periodic table shown during a Next Generation episode, it has the chemical symbol Dt and the atomic number 87, which in reality belongs to francium.
In the real world, dilithium (Li2) is a molecule composed of two covalently bonded lithium atoms.
Dilithium is depicted as an extremely hard crystalline mineral that occurs naturally on some planets. When placed in a high-frequency electromagnetic field, eddy currents are induced in its structure which keep charged particles away from the crystal lattice. This prevents it from reacting with antimatter when so energized, because the antimatter particles never actually touch it. Therefore, it is used to contain and regulate the annihilation reaction of matter and antimatter in a starship's warp core, which otherwise would explode from the uncontrolled annihilation reaction. Though low-quality artificial crystals can be grown or replicated, they are limited in the power of the reaction they can regulate without fragmenting, and are therefore largely unsuitable for warp drive applications. Due to the need for natural dilithium crystals for interstellar travel, deposits of this material are, much like real-world equivalents such as oil, a highly contested resource, and as such, dilithium crystals have led to more interstellar conflict than all other reasons combined.
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