From Wikipedia, the free encyclopedia
Jump to: navigation, search
Category Phosphate minerals
(repeating unit)
Strunz classification 8.EB.35
Crystal system Monoclinic
Crystal class Prismatic (2/m)
(same H-M symbol)
Space group C2/c
Unit cell a = 12.45(6) Å, b = 12.96(3) Å,
c = 17.22(5) Å; β = 105.7°; Z = 4
Formula mass 489.01 gram/mol
Color Pale creamy yellow
Crystal habit As lathlike to platy grains, in microcrystalline aggregates seams and crusts.
Mohs scale hardness 1-2
Luster Adamantine - pearly
Streak White
Diaphaneity Translucent
Specific gravity 2.70
Optical properties Biaxial (-)
Refractive index nα = 1.550 nβ = 1.588 nγ = 1.590
Birefringence δ = 0.040
Pleochroism X = colorless; Y = Z = pale yellow. Orientation: Y = elongation of laths with positive elongation; Y at 8°-25° to elongation of laths with negative elongation.
2V angle Measured: 28° to 43°, Calculated: 24°
Other characteristics Radioactive
References [1][2][3]

Coconinoite is a uranium ore that was discovered in Coconino County, Arizona. It is a phosphate mineral; or uranyl phosphate mineral along with other subclass uranium U6+ minerals like blatonite, boltwoodite, metazeunerite and rutherfordine.


The chemical formula is Fe2Al2(UO2)2(PO4)4(SO4)4(OH)2·20H2O.[4] The chemical formula was derived from the spectrographic analysis.[4]

Physical properties[edit]

The mineral has a white streak and a pale creamy yellow color. The mineral occurs as microscopic crystals, the largest found is 6 by 20 micrometers. It is a radioactive mineral, but not fluorescent.[4] Upon heating for dehydration it is found that the mineral loses some of its SO2 at 600 to 800 °C.

Geologic occurrence[edit]

It occurs in the oxidized zone of vanadium-poor Colorado Plateau-type uranium deposits of Utah and Arizona. It occurs in association with gypsum, jarosite, limonite, quartz, clay minerals and coalized wood at the Jomac mine, Utah.[3]

Coconinite was first described in 1966 for occurrences in the Huskon Mines, Cameron, Cameron District and the Sun Valley Mine, Vermillion Cliffs District, Coconino County, Arizona. It was named for Coconino County.[2]


  1. ^ Webmineral data
  2. ^ a b
  3. ^ a b Handbook of Mineralogy
  4. ^ a b c Young.E, Weeks, A.D, and Merowitz, R. (1996) Coconinoite a new mineral from Utah and Arizona. The American Mineralogist 51, 651-663