Calaverite (AuTe2) in purple fluorite vein, Cripple Creek Diatreme (Early Oligocene, 32 Ma), central Colorado 2
Calaverite (AuTe2) (gold-colored) in a purple fluorite vein, from the Cripple Creek Diatreme (Early Oligocene, 32 Ma) of central Colorado, USA.
The Cripple Creek Gold District of central Colorado, USA is famous for its unusual gold and silver mineralization. Precious metal mineralization occurs in the Cripple Creek Diatreme, the root zone of a deeply eroded volcano dating to the Early Oligocene (32 Ma).
The dominant lithology at Cripple Creek is the scarce igneous rock phonolite, an alkaline, intermediate, extrusive igneous rock. Cripple Creek gold can be found in its native state (Au), but it typically occurs in the form of gold telluride minerals (for example, sylvanite - (Au,Ag)2Te4, calaverite - AuTe2, petzite - Ag3AuTe2, krennerite - (Au,Ag)Te2, and nagyagite - Pb5Au(Sb,Bi)Te2S6). Silver also occurs in some Cripple Creek minerals, including sylvanite, petzite, krennerite, hessite - Ag2Te, tennantite - (Cu,Ag,Fe,Zn)12As4S13, acanthite - Ag2S, and tetrahedrite - (Cu,Fe,Ag,Zn)12Sb4S13.