Ichnusaite (pronounced iknusa-ait) is a very rarely found mineral.[3] Ichnusaite is a natural compound of thorium and molybdenum with the formula Th(MoO4)2·3H2O. It was discovered in Su Seinargiu, Sarroch, Cagliari, Sardegna, Italy in 2013.[2] The name is from the old Greek name of Sardinia, Ιχνουσσα, Ichnusa.[5]
This locality is also a place of discovery of the second natural thorium molybdate - nuragheite.[6]

Ichnusaite
General
CategoryMolybdate minerals
Formula
(repeating unit)
Th(MoO4)2•3H2O
IMA symbolIch[1]
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
(same H-M symbol)
Space groupP21/b
Unit cella = 9.68, b = 10.38
c = 9.38 [Å], β = 90.00° (approximated)
Z = 4
Identification
ColorColorless
Cleavage{100}, perfect
TenacityBrittle
LusterPearly adamantine
Other characteristics Radioactive
References[2][3][4]

Occurrence and association

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Muscovite, nuragheite, and xenotime-(Y) are the associates of ichnusaite.[2]

Notes on chemistry

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Ichnusaite is chemically pure.[2]

Crystal structure

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The main features of the crystal structure of ichnusaite are:[2]

  • electroneutral Th(MoO4)2(H2O)2 (100) sheets
  • ThO7(H2O)2 and MoO4 polyhedra polymerize to give the above sheets
  • sheets are stacked along [100] and held by hydrogen bonds

Bibliography

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References

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  1. ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. ^ a b c d e Orlandi, Paolo; Biagioni, Cristian; Bindi, Luca; Nestola, Fabrizio (2014-10-01). "Ichnusaite, Th(MoO4)2·3H2O, the first natural thorium molybdate: Occurrence, description, and crystal structure". American Mineralogist. 99 (10): 2089–2094. doi:10.2138/am-2014-4844. ISSN 0003-004X. S2CID 97061833. Archived from the original on 2016-05-21. Retrieved 2016-02-13.
  3. ^ a b "Ichnusaite- Mindat.org". Mindat.org. Retrieved 2016-03-06.
  4. ^ Mineralienatlas
  5. ^ "Ichnusaite". www.mindat.org. Retrieved 2021-05-07.
  6. ^ "Nuragheite - Mindat.org". Mindat.org. Retrieved 2016-03-06.