Trimonite was the hardest material known to humans. It was 15 times harder than diamond and extremely rare. The planet LV-178 contained trimonite, and was the site of many mining operations to collect the mineral for conventional use.
- Alien: Out of the Shadows/audio drama
- Alien: Sea of Sorrows
- Predator: Incursion (mentioned only)
- Alien: River of Pain (audio drama) (mentioned only)