Outstanding cluster of sharp, modified octahedrons of Betafite, from Madagascar. The reddish brown crystals have a waxy luster, excellent form, and just a small amount of edge wear. The largest of these Betafites is 2.3 cm on edge. Betafite is now considered a variety of the Pyrochlore Supergroup, and revisions of the supergroup occur as chemical analyses refine the mineral definitions (per MINDAT: An isometric mineral, (Ca,Na,U)2 (Ti,Nb,Ta)2 O6 (OH); pyrochlore group; forms a series with pyrochlore; nowadays obsolete name originally assigned to members of the series having uranium greater than 15%; radioactive; in granitic pegmatites). This cluster contains attractive, textbook examples of this mineral from its most famous old locality, the namesake locality! It was illustrated in Mineralogical Record in 2007: https://goo.gl/tyuH7N