Fergusonite is a mineral comprising a complex oxide of various rare earth elements. Its formula is given basically as (Ce,La,Nd)NbO4. However other analyses also include yttrium, erbium, and tantalum. It is found as small (less than 100 micrometres), needle-like crystals in pegmatite. It was named after British Politician and mineral collector Robert Ferguson of Raith (1767 – 1840)