The Mineral META-ANKOLEITE

  • Chemistry: KUO2PO4 - 3H2O, Hydrated Potassium Uranyl Phosphate
  • Class: Phosphates
  • Group: Meta-autunite
  • Uses: A very minor ore of uranium and as mineral specimens.
  • Specimens

Meta-ankoleite was thought to be a dehydration product of the mineral, ankoleite, hence the name. Ankoleite is no longer recognized as a mineral or never was really established, but in any case it leaves meta-ankoleite without a corresponding non-meta-mineral. Meta is Latin for changed as in changed-ankoleite. This prefix is used when minerals have slightly altered from one mineral to another by natural processes and the mineralogist whom identifies the new mineral feels that the meta prefix would be appropriate. In this case as in the case of many of the other members of the Meta-autunite Group, the change occurs with the dehydration of the original mineral into a new mineral. Often the loss of a water molecule or two is not significant, but in these phosphate minerals it has been found to be telling. However with meta-ankoleite it is the original mineral so its name is somewhat of a misnomer. It is still placed in the Meta-autunite Group because of its structural similarities to these other minerals.

The structure of meta-ankoleite is composed of flattened phosphate tetrahedrons linked to uranium-oxygen groups that form distorted octagons. The phosphate and uranium groups form sheets that are weakly held together by water molecules. This structure produces the tabular habit, the one perfect direction of cleavage, and the relative softness. It is an analogous structure to that of the phyllosilicates. The flattened tetrahedrons have a near four fold symmetry and the distorted octagons contribute to the tetragonal symmetry.

Meta-ankoleite is one of several fluorescent minerals from the fluorescent mineral capital of the world at Sterling Hill, New Jersey, USA. It fluoresces a green color there under shortwave ultraviolet light. At meta-ankoleite's type locality in the Ankole District, Uganda specimens fluoresce a yellow-green color under both shortwave and longwave radiation. Remember, this is a radioactive mineral and should be stored away from other minerals that are affected by radioactivity and human exposure should always be limited.

PHYSICAL CHARACTERISTICS:

  • Color is yellow.
  • Luster is vitreous to dull.
  • Transparency: Crystals are translucent to transparent.
  • Crystal System is tetragonal; 4/m 2/m 2/m.
  • Crystal Habits include platy square crystals. Also as crusts, micaceous, foliated and earthy.
  • Cleavage is perfect in one direction.
  • Fracture is uneven.
  • Hardness is 2 - 2.5
  • Specific Gravity is approximately 3.5 (above average for translucent minerals).
  • Streak is a pale yellow.
  • Other Characteristics: Radioactive and fluorescent yellow-green or green.
  • Associated Minerals include quartz, muscovite, phosphuranylite and uranium minerals.
  • Notable Occurrences include the type locality of Mungenyi Pegmatite, Ankole District (hence the name), Uganda and at Sterling Hill, New Jersey, USA.
  • Best Field Indicators are color, crystal habit, fluorescence, radioactivity, associations, cleavage and brittle cleavage sheets.

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