Kellinite was a material used in starship construction.
Ensign Harry Kim insisted on using kellinite for the hull of the Delta Flyer during its construction in 2375. Lieutenant Tuvok believed this a poor choice. (VOY episode: "Extreme Risk")
During the Dominion War, the Federation government initiated a trade agreement with Aligar for kellinite, despite that planet's use of slave labor for mining the material. (ST novel: Articles of the Federation)
The IKS Gorkon determined that the planet San-Tarah, visited in 2376, was a rich in kellinite deposits. (GKN novels: A Good Day to Die, Honor Bound)