Nickel

Nickel is an element, atomic number 28 on the 21st century periodic table.

The water of a Class M planet surveyed by Nog and Jake Sisko in 2370 contained traces of nickel, copper and birythium. 

Many planetary cores are composed of an iron-nickel alloy, either in solid or liquid form.

The planetoid in the Gamma Canaris region where Zefram Cochrane lived with the Companion is composed of iron and nickel. 

A M-class planet located in the Ngame Nebula that was terraformed by the Paxans and discovered by the USS Enterprise (NCC-1701-D) had a nickel-iron core. 

Sensor scans of the asteroids artificially constructed by the Etanians, used to attack a Nezu colony, were composed of a simple nickel-iron composite. 

A planet that the Delta Flyer crashed on in 2375 had a Class M atmosphere, nickel-iron core, and bemonite mantle.