Allanite in its host rock. Allanite, also known as orthite, is a sorosilicate mineral. It is one of the most ubiquitous rare earth minerals known and an important ore for a number of rare earth elements, like cerium, lanthanum, yttrium and thorium. It is usually black with a high lustre. This specimen, from Arendal, Norway, measures 120 millimetres wide.