It is also found in the contact metamorphic marbles that surround these pegmatites. Although concerning the marbles there is a question as to whether they are actually the product of igneous carbonatites. At these and other localities, betafite is associated with several minerals common to these rocks such as quartz , feldspars , columbite , tantalite , zircon , biotite , thorite , allanite , fergusonite and other rare earth minerals. Betafite is a popular and interesting mineral. Although lacking in color, it makes up for it in the large well formed crystals for which it is known.
Color is black with a tint of yellow, brown or green.
Luster is earthy to metallic and sometimes vitreous when translucent. Crystals are generally opaque but some translucent specimens are known. Some crystals can be quite large and can weigh up to and slightly over 100 kg. Cleavage is absent. Fracture is conchoidal.