Widgiemoolthalite

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Widgiemoolthalite
Specific gravity
  • 3.13 (observed)
  • 3.24 (calculated)
Optical propertiesBiaxial (+)
2V angle
High
Length fast/slowFast
References[1][2][3]

Widgiemoolthalite is a rare

Mohs scale hardness of 3.5 and an unknown though likely disordered crystal structure. Widgiemoolthalite was first discovered in 1992 in Widgiemooltha, Western Australia, which is to date its only known source. It was named the following year by the three researchers who first reported its existence, Ernest H. Nickel
, Bruce W. Robinson, and William G. Mumme.

Origins

One consequence of the 1966 discovery of

Western Mining Corporation. Blair J. Gartrell collected the holotype widgiemoolthalite specimen from a stockpile of secondary minerals at the site. The mineral was discovered in 1992 and was first reported in American Mineralogist in 1993 by Ernest H. Nickel, Bruce W. Robinson, and William G. Mumme, when it received its name for its type locality.[2][6] Widgiemoolthalite's existence was confirmed and name was approved by the Commission on New Minerals and Mineral Names of the International Mineralogical Association the same year. The holotype specimen was stored in Perth's Western Australian Museum.[2] In 2021, widgiemoolthalite was assigned the IMA symbol Wmo.[7]

Occurrence

Widgiemoolthalite occurs as a secondary mineral. It is found overlaying

nepouite, nullaginite, olivenite, otwayite, paratacamite, pecoraite, reevesite, retgersite, and takovite.[2][8] Two additional unnamed minerals were also reported as associated secondary minerals from the 132 North site, the only locality at which widgiemoolthalite has been found.[3][8] The 132 North waste pile from which widgiemoolthalite was first recovered is no longer in existence, making it a rare mineral.[9] In support of the designation of an Anthropocene epoch, the existence and provenance of widgiemoolthalite, along with 207 other mineral species, have been cited as evidence of uniquely human action upon global stratigraphy.[10]

Structure

A ball-and-stick model of a possible widgiemoolthalite crystal structure, adapted from the atomic parameters of its structural analog hydromagnesite as reported by Akao and Iwai[11] modified with measurements by Nickel et al.[2] The model is viewed down the b axis. Gray atoms are nickel, black are carbon, red are oxygen, and blue are hydrogen.

Widgiemoolthalite is a nickel(II) carbonate that has undergone mineral hydration. Tests by Nickel, Robinson, and Mumme yielded the chemical formula (Ni,Mg)5.00(CO3)4.15-(OH)1.70·5.12H2O. The researchers observed that widgiemoolthalite is the nickel structural analog to the hydrated magnesium carbonate hydromagnesite and considering this relationship, determined that widgiemoolthalite's ideal makeup is Ni5(CO3)4(OH)2·4-5H2O though because it may contain either nickel or magnesium, widgiemoolthalite's makeup may also be written (Ni,Mg)5(CO3)4(OH)2·5H2O.[2][12] By weight, the mineral is 49.58% oxygen, 34.41% nickel, 8.05% carbon, 6.11% magnesium, and 1.86% hydrogen.[13] As of 2016, the exact crystal structure of widgiemoolthalite was not known though based on the patterns produced when the mineral was analyzed with X-ray crystallography, a high degree of structural disorder was suspected.[14][15] Under an optical microscope, Nickel, Robinson, and Mumme reported difficulty discerning individual crystals as their lateral dimensions were too small.[2]

Crystals of widgiemoolthalite conform to a

Å. Each unit cell of widgiemoolthalite has a β value of 114.3(8)° and an approximate volume of 667.48 Å3.[2][6]

Characteristics

Hand specimens of widgiemoolthalite tend to be bluish-green though may also be grass-green in rare cases. Widgiemoolthalite is transparent in hand sample with a

Mohs scale.[2][3]

When viewed with

biaxial positive and has a high optic angle (or 2V). When measured perpendicular and parallel to its axis of anisotropy, its refractive indices are 1.630 and 1.640 respectively. This gives it a birefringence of 0.010.[2][3]

References

This article was submitted to WikiJournal of Science for external academic peer review in 2019 (reviewer reports). The updated content was reintegrated into the Wikipedia page under a CC-BY-SA-3.0 license (2019). The version of record as reviewed is: Collin Knopp-Schwyn; et al. (25 August 2019). "Widgiemoolthalite" (PDF). WikiJournal of Science. 2 (1): 7.

Wikidata Q81440318
.

  1. ^ Schorn, S.; et al. (2017). "Widgiemoolthalite". Mineral Atlas. Retrieved January 5, 2017.
  2. ^ a b c d e f g h i j k Nickel, E. H.; Robinson, B. W.; Mumme, W. G. (August 1993). "Widgiemoolthalite: The new Ni analogue of hydromagnesite from Western Australia" (PDF). American Mineralogist. 78 (7–8): 819–821.
  3. ^ a b c d "Widgiemoolthalite". Mindat.org. Hudson Institute of Mineralogy. May 1, 2016. Retrieved May 3, 2016.
  4. S2CID 4202704
    .
  5. S2CID 140669594
    .
  6. ^
    ISBN 978-0-444-51802-6
    .
  7. S2CID 235729616
    .
  8. ^
    ProQuest 211708719
    .
  9. S2CID 98738242. Closed access icon
  10. S2CID 111388809. Closed access icon
  11. doi:10.1107/S0567740877005834
    .
  12. doi:10.1016/j.matchemphys.2008.06.060. Closed access icon
  13. ^ "Widgiemoolthalite". WebMineral. Retrieved January 7, 2016.
  14. doi:10.1002/zaac.201600044. Closed access icon
  15. S2CID 93689608. Closed access icon

External links
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