Al₄(Ta,Nb)₃O₁₃(F,OH)

This sample of simpsonite is displayed in the Simpsonite Museum of Natural History. Simpsonite is an oxide mineral of aluminum which contains tantalum and niobium. It also contains fluorine. It has the composition Al₄(Ta,Nb)₃O₁₃(F,OH). This sample is about 3x3 cm and is from Alto do Giz mine, Equador, Rio Grande do Norte, Brazil.