Ichnusaite Explained

Ichnusaite
Category:	Molybdate minerals
Formula:	Th(MoO4)2•3H2O
Imasymbol:	Ich^[1]
System:	Monoclinic
Class:	Prismatic (2/m) (same H-M symbol)
Symmetry:	P21/b
Unit Cell:	a = 9.68, b = 10.38 c = 9.38 [Å], β = 90.00° (approximated) Z = 4
Color:	Colorless
Cleavage:	, perfect
Tenacity:	Brittle
Luster:	Pearly adamantine
Other:	Radioactive
References:	^[2]

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.^[4] 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]

Occurrence and association

Muscovite, nuragheite, and xenotime-(Y) are the associates of ichnusaite.^[4]

Notes on chemistry

Ichnusaite is chemically pure.^[4]

Crystal structure

The main features of the crystal structure of ichnusaite are:^[4]

• 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

• Orlandi, P., Biagioni, C., Bindi, L. und Nestola, F. (2013) Ichnusaite, IMA 2013- 087. CNMNC Newsletter No. 18, December 2013, page 3255; Mineralogical Magazine, 77, 3249-325
• http://rruff.geo.arizona.edu/AMS/result.php?mineral=Ichnusaite
• https://web.archive.org/web/20160521090233/http://ammin.geoscienceworld.org/content/99/10/2089
• https://arpi.unipi.it/handle/11568/638691#.Vr93OUKuAt4
• http://www.degruyter.com/dg/viewarticle/j$002fammin.2014.99.issue-10$002fam-2014-4844$002fam-2014-4844.xml
• https://www.bbc.com/news/science-environment-35569659

Notes and References

1. Warr. L.N.. 2021. IMA–CNMNC approved mineral symbols. Mineralogical Magazine. 85. 3. 291–320. 10.1180/mgm.2021.43. 2021MinM...85..291W. 235729616. free.
2. https://www.mineralienatlas.de/lexikon/index.php/MineralData?mineral=Ichnusaite Mineralienatlas
3. Web site: Ichnusaite- Mindat.org . Mindat.org . 2016-03-06.
4. Ichnusaite, Th(MoO4)2·3H2O, the first natural thorium molybdate: Occurrence, description, and crystal structure. American Mineralogist. 2014-10-01. 0003-004X. 2089–2094. 99. 10. 10.2138/am-2014-4844. en. Paolo. Orlandi. Cristian. Biagioni. Luca. Bindi. Fabrizio. Nestola. 97061833. 2016-02-13. https://web.archive.org/web/20160521090233/http://ammin.geoscienceworld.org/content/99/10/2089. 2016-05-21. dead.
5. Web site: Ichnusaite. 2021-05-07. www.mindat.org.
6. Web site: Nuragheite - Mindat.org . Mindat.org . 2016-03-06.