Phosphorus

Phosphorus is a non-metalic chemical element. One form of phosphorus emits a faint glow.

Liquid phosphorus comprised one of the atmospheric layers of a Class 7 gas giant planet discovered by the in 2151. 

Crystals found on the USS Exeter (NCC-1672) in 2268 were comprised of 35% potassium, 18% carbon, 1.5% calcium and 1% phosphorus – all elements found in the Human body. It was later determined that the crystals were in fact the remains of the Exeter crew.