Extremely rare. Second oxidation zone. Third oxidation zone (?)
- 2nd Oxidation Zone
- 3rd Oxidation Zone
Paragenetic and General Notes
Powellite occurs as small, straw-yellow tetragonal crystals on scorodite with tennantite, with powellite crystals to 3 mm (Pinch and Wilson, 1977). Gerdtremmelite is also part of this paragenesis (Gebhard, 1999).
Powellite forms a series with scheelite (CaWO4), and crystals of intermediate composition (c. 60% scheelite : 40% powellite) have been analysed recently on a specimen in the collection of Mark Feinglos (personal communication to M.Southwood, September, 2015). These golden-brown, pseudo-octahedral crystals, to a few mm in size, are associated with quartz and fraiponite, on a sulphide matrix.