This sample of tennantite-tetrahedrite is displayed in the Smithsonian Museum of Natural History. A common name for this mineral is "fahlore". Tennantite-tetrahedrite is a sulfide mineral of copper, iron, arsenic and antimony. The minerals tennantite and tetrahedrite form a series of composite minerals with the series formula Cu6[Cu4(Fe,Zn)2]As4S13- Cu6[Cu4(Fe,Zn)2]Sb4S13. The composition of this sample is labeled (Cu,Fe)12(As,Sb)4S13 . The sample is about 20x18 cm and is from El Cobre, Chihuahua, Mexico . This sample is formed with quartz.