Coltan is a metallic alloy used in the creation of the endoskeletal structure of Terminators. Specifically, it is used in the manufacturing of the non-liquid metal units such as the T-800 and the T-888 series Terminators. Coltan was ideal for its high melting point, providing better resistance to heat for the T-800 and T-888s than the Titanium alloy endoskeletons such as those used by the earlier T-600 models. The alloy was utilized by Skynet in the early days of the War Against the Machines.
In 2007, Cameron Phillips learned about a shipment of Coltan that had been re-routed from Oakland to the Port of Los Angeles. Cameron, Sarah Connor and John Connor sneaked into the port warehouse only to find that the regular workers had been replaced with mercenaries employed by a Terminator. They hijacked numerous crates of Coltan - enough to create 539 Terminator units.