• Chemistry: CaMoO4, Calcium Molybdenate
  • Class: Sulfates
  • Subclass: Molybdenates
  • Uses: As a minor ore of molybdenum (an important industrial metal) and as mineral specimens.
  • Specimens

Powellite is one of only a handful of relatively common molybdenum minerals. Other molybdenum minerals include wulfenite, molybdenite, ferrimolybdite, molybdite and sidwellite. Powellite is named for the American geologist, Major John Wesley Powell, a former director of the U. S. Geological Survey. Most of powellite's occurrences are the result of hydrothermal reactions with the primary sulfide mineral molybdenite, with a formula of MoS2. Powellite in fact, forms pseudomorphs after molybdenite. A pseudomorph is an atom by atom replacement of one mineral's chemistry for another; all the while the crystal retains the outward shape of the original mineral (pseudomorph means "false shape"). These pseudomorphs will have the shape of molybdenite crystals, but are actually made of powellite. Powellite also is known to form as a primary mineral in quartz veins.

Powellite forms an incomplete series with the mineral scheelite, CaWO4. Scheelite differs from powellite by the substitution of the molybdenum in powellite by the tungsten (W) in scheelite. Some tungsten is usually found in powellite and thus sometimes the formula of powellite is written as Ca(Mo, W)O4 to reflect this substitution. Scheelite is a popular fluorescent mineral as it typically glows a bright bluish white. Powellite is less well known for its fluorescence, but some specimens can display a delightful golden yellow under ultraviolet light. Crystals of powellite resemble the much more common but heavier crystals of scheelite, fortunately the difference in fluorescence is a key to distinguishing them. Powellite, scheelite and the silicate mineral scapolite all belong to an exclusive symmetry class called the Tetragonal Dipyramidal Class with a symmetry of 4/m.


  • Color is yellow, brown, gray, blue, white or black.
  • Luster is adamantine to greasy.
  • Transparency: Crystals are translucent to transparent.
  • Crystal System is tetragonal; 4/m
  • Crystal Habits include small four sided pyramidal crystals (pseudo-octahedral) and thin plates. Commonly as crusts or films around altered molybdenite and as pseudomorphs after molybdenite.
  • Cleavage is distinct in four directions (bipyramidal).
  • Fracture is uneven.
  • Hardness is 3.5 - 4.
  • Specific Gravity is approximately 4.2 - 4.3 (heavy for nonmetallic minerals).
  • Streak is white.
  • Other Characteristics: Fluorescent golden yellow.
  • Associated Minerals are quartz, zeolites, molybdenite and lindgrenite.
  • Notable Occurrences include the Peacock Lode, Seven Devils district, Idaho (the type locality); Keewenaw Peninsula, Michigan; Tungsten, Nevada; Superior, Arizona and Randsberg, California, USA; Nasik, India; Turkey; Russia; Scotland; Clayton Quarry, Panama Canal Zone, Panama and Morocco.
  • Best Field Indicators are crystal habit, color, fluorescence, association with molybdenite and cleavage.
POWELLITE specimens:
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POWELLITE specimen pow-1
$ 69.00
Dims:2.1x1.6x1.2" (5.3x4.1x3.0 cm)
Wt: 2.2oz. (63g)
Nasik, Maharashtra st., India
This wonderful little specimen consists of a double terminated crystal of powellite resting upon a mass of intergrown powellite and natrolite crystals. Some of the needles of natrolite grow up through the powellite crystal and extend 1.0" (2.5cm) above it. This specimen fluoresces brilliant yellow under both short and long wave ultraviolet light. There is no visible damage to this specimen; it is affixed to a clear acrylic base with sticky-tack.
no photo
pow-1 ($ 69.00)
Nasik, Maharashtra st., India
POWELLITE specimen pow-2
$ 30.00
Dims: 0.76x0.64x0.45" (1.93x1.63x1.14cm)
Wt: 30.5ct (6.10g)
Nasik, India
This powellite specimen is an incomplete crystal, showing only two good crystal faces, one side that looks like a cleavage plane, and the remaining surfaces, while not looking like damage, they are not flat crystal faces but rather have an irregular surface where the growth pattern was likely interrupted by something in the way. This specimen glows a pretty yellow color under shortwave ultraviolet. The powellite is transparent, but has so many internal fractures as to appear only translucent.
no photo
pow-2 ($ 30.00)
Nasik, India
POWELLITE specimen pow-3
$ 75.00
Dims: 1.51x0.98x0.83" (3.83x2.48x2.12cm)
Wt: 0.89oz (25.1g)
Nasik, India
This is a good specimen of powellite. The crystal is incomplete, showing only three faces. The remaining surfaces appear to be growth patterns or possibly contact imprints, except for an area of damage on the bottom. There is a very nice (unfortunately incomplete) arrowhead face on one side, which suggests that the complete crystal would have had a similar shape. The crystal faces show distinct striations. The powellite is transparent and pale yellow, with many internal fractures. And of course this powellite fluoresces a bright yellow under UV (very bright with long wave).
no photo
pow-3 ($ 75.00)
Nasik, India
POWELLITE specimen pow-4
$ 40.00
Dims: 0.80x0.65x0.40" (2.02x1.64x1.01cm)
Wt: 0.25oz (7.0g)
Nasik, India
This specimen of powellite is transparent and nearly colorless, with the merest hint of yellow for a color. Only two surfaces are original crystal faces, and these show relatively deep striations and a vitreous luster. All other surfaces look like fracture. The interior is also cloudy due to internal fractures. This specimen fluoresces a brilliant yellow under both LW and SW UV (but brighter under LW).
no photo
pow-4 ($ 40.00)
Nasik, India


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