Class : Sulfates, chromates, molybdates
    Subclass : Molybdates
    Crystal system : Tetragonal
    Chemistry : CaMoO₄
    Rarity : Uncommon to rare

Powellite forms a discontinuous isomorphic series with scheelite, by replacing part of the molybdenum with tungsten (up to 10% of WO₃). It is a rare calcium molybdate whose mode of formation is not clearly established. It can be of secondary origin, forming by alteration of molybdenite which it can replace (pseudomorph), or have a primary hydrothermal origin of high (scheelite and molybdenite skarns) or low temperature (basalt vacuoles associated with zeolites). It was named in honor of Major John Wesley Powell, American geologist, ethnologist and explorer. Powellite is transparent to translucent, with a strong adamantine luster, yellowish white to yellowish gray, or yellowish brown to orange yellow. It is rarely crystallized in pyramids or tetragonal octahedra reminiscent of scheelite. Powdery powellite or laminated pseudomorph results from the transformation of molybdenite. It exhibits a yellow fluorescence under short wave UV light.

Main photo : Powellite on stilbite from Aurangabad, Maharashtra, India

No twins known for this mineral species.

No fakes listed for this mineral species.