Ichnusait

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Ichnusait
General and classification
other names

IMA 2013-087

chemical formula Th [MoO 4 ] 2 • 3H 2 O
Mineral class
(and possibly department) 		Sulfates (including selenates, tellurates, chromates, molybdates, and tungstates)
Similar minerals Nuragness
Crystallographic Data
Crystal system monoclinic
Crystal class ; symbol monoclinic prismatic; 2 / m
Space group P 2 1 / c (No. 14)Template: room group / 14
Lattice parameters a  = 9.6797  Å ; b  = 10.3771 Å; c  = 9.3782 Å
β  = 90.00 (1) °
Physical Properties
Mohs hardness not defined
Density (g / cm 3 ) calculated: 4.262
Cleavage completely after {100}
Break ; Tenacity brittle
colour colorless, white
Line color White
transparency transparent
shine Diamond luster, pearlescent luster
radioactivity radioactive

Ichnusaite is a very rarely occurring mineral from the mineral class of "sulfates (including selenates, tellurates, chromates, molybdates and tungstates)" with the chemical composition Th [MoO 4 ] 2 · 3H 2 O and thus chemically a hydrous thorium - molybdate . Ichnusaite is also the first find of a naturally formed thorium molybdate worldwide.

Ichnusaite crystallizes in the monoclinic crystal system , but has so far only been discovered in the form of microscopic, tabular crystals with a maximum length of 200  μm . The crystals are colorless and transparent with a diamond-like sheen on the surfaces. In the form of leafy mineral aggregates , the mineral also appears white with a pearlescent sheen.

Etymology and history

Ichnusaite was found together with nuragheit (Th [MoO 4 ] 2 · H 2 O) rather by chance during a routine check of mineral samples from an experimental mining of a molybdenum-bismuth ore deposit in the mine of Punta de su Seinargiu (also Su Seinargiu , 39 ° 4 ′ 53 ″  N , 8 ° 58 ′ 37 ″  E ), which is located in the uninhabited western part of the municipality of Sarroch on the Italian island of Sardinia . In a qualitative EDS analysis , it was found that some crystals only contained thorium and molybdenum . Since natural thorium molybdates were previously unknown, a team of mineralogists consisting of Paolo Orlandi, Cristian Biagioni, Luca Bindi and Fabrizio Nestola tried to fully analyze the new compound. Using two particularly pure grains of the mineral, the chemistry and crystal structure of the mineral could finally be determined.

The team of mineralogists borrowed the name for the new mineral from the old Greek name Ιχνουσσα [ichnusa] for the island of Sardinia. The full mineral description and the chosen name was submitted to the International Mineralogical Association (IMA) for review (IMA accession number: 2013-087) and approved in the same year.

The type material of the mineral is in the collection in the Museo di Storia Naturale of the University of Pisa in Italy under the catalog no. Saved in 19679.

classification

Ichnusaite was only recognized and published by the IMA in 2013 as an independent mineral. An exact group assignment in the 9th edition of the Strunz'schen mineral systematics , the last update of which was carried out with the publication of the IMA list of mineral names in 2009, is therefore not yet known. Based on its chemical identity as molybdate, which is related to sulfates , the mineral can be assumed to be classified within Division 7.G Molybdates and tungstates within the class of "sulfates (including selenates, tellurates, chromates, molybdates, and tungstates)" will be.

Crystal structure

Ichnusaite crystallizes monoclinically in the space group P 2 1 / c (space group no. 14) with the lattice parameters a  = 9.6797 (12)  Å ; b  = 10.3771 (13) Å; c  = 9.3782 (12) Å and β = 90.00 (1) ° and 4 formula units per unit cell . Template: room group / 14

properties

The mineral is radioactive due to its thorium content of up to 38.29% .

Education and Locations

Ichnusaite was likely formed by converting molybdenum ores under basic conditions. It was found to be intimately fused with the closely related nuragness in drusen of quartz veins, which was also first discovered in the mine of Punta de su Seinargiu . Muscovite and partially corroded xenotime (Y) appeared as additional accompanying minerals .

Ichnusait and nuragheit could only be discovered at their type locality Punta de Su Seinargiu on Sardinia. In addition to the minerals already mentioned, the mine is also type locality for Sardignait (2008), Gelosaite and Tancait- (Ce) (2009), Mambertiit (2013) and Suseinargiuit (2014).

Precautions

Due to the ionizing radiation , mineral samples from Ichnusait should only be kept in dust- and radiation-proof containers, but especially never in living rooms, bedrooms or work rooms. Absorption into the body ( incorporation , ingestion ) should also be prevented in any case and, for safety, direct body contact should be avoided and face masks and gloves should be worn when handling the mineral.

See also

literature

  • Ichnusaite, IMA 2013-087. In: CNMNC Newsletter No. 18 October and November 2013, p. 10 ( PDF 170.7 kB )
  • Paolo Orlandi, Cristian Biagioni, Luca Bindi, Fabrizio Nestola: Ichnusaite, Th (MoO4) 2 · 3H2O, the first natural thorium molybdate: Occurrence, description, and crystal structure In: American Mineralogist Volume 99, 2014, pp. 2089–2094 ( available online at researchgate.net )

Web links

Individual evidence

  1. ↑ Stefan Weiß: The large Lapis mineral directory. All minerals from A - Z and their properties . 6th completely revised and supplemented edition. Weise, Munich 2014, ISBN 978-3-921656-80-8 .
  2. ↑ a b c d Paolo Orlandi, Cristian Biagioni, Luca Bindi, Fabrizio Nestola: Ichnusaite, Th (MoO4) 2 3H2O, the first natural thorium molybdate: Occurrence, description, and crystal structure In: American Mineralogist Volume 99, 2014, p 2089–2094 (available online at researchgate.net )
  3. ↑ Ichnusaite, IMA 2013- 087. In: CNMNC Newsletter No. 18 October and November 2013, p. 10 ( PDF 170.7 kB )
  4. ↑ IMA / CNMNC List of Mineral Names September 2009 (PDF 1.8 MB with the last official Strunz classification)
  5. ↑ Find location list for Ichnusait at the Mineralienatlas and at Mindat
  6. ↑ Mineralienatlas : type locality Su Senargiu mine and Mindat.org: Punta de Su Seinargiu (Su Seinargiu; Su Senargiu), Sarroch, Cagliari Province, Sardinia, Italy

Coordinates: 39 ° 4 ′ 53 ″  N , 8 ° 58 ′ 37 ″  E