Anzaite-(Ce)

Anzaite-(Ce) is a rare-earth element (REE) oxide mineral with the formula Ce4Fe2+Ti6O18(OH)2.[1][2] An example of chemically related mineral is lucasite-(Ce),[3] although it contains no iron. Cerium in anzaite-(Ce) is mainly substituted by neodymium, lanthanum, calcium and praseodymium. Titanium is substituted by niobium. Trace elements include thorium. The mineral is monoclinic, space group C2/m. Anzaite-(Ce) is hydrothermal mineral found in a carbonatite from the mineralogically-prolific Kola Peninsula. The mineral name honors Anatoly N. Zaitsev, who is known for studies of carbonatites and REE.[1][2]

Anzaite-(Ce)
General
CategoryOxide mineral
Formula
(repeating unit)		Ce4Fe2+Ti6O18(OH)2
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
(same H-M symbol)
Space groupC2/m
Unit cella = 5.29, b = 14.58
c = 5.23 [Å]; β = 97.23° (approximated); Z = 1
Identification
ColorGrey
Crystal habitCrystals (tiny)
CleavageNone
TenacityBrittle
Mohs scale hardness6–6.5
DiaphaneityOpaque
Density5.05 (calculated; approximated)
References[1][2]

Occurrence and association

Parent rocks for anzaite-(Ce) are silicocarbonatites of the Afrikanda alkali-ultramafic massif. These rocks underwent hydrothermal reworking, that beside anzaite-(Ce) produced also calcite, clinochlore, hibschite and titanite in expense of primary minerals.[1]

Notes on chemistry

Cerium in anzaite-(Ce) is substituted by significant amounts of neodymium, lanthanum, calcium, and praseodymium, with minor samarium and thorium. Other impurities in the mineral composition include niobium and silicon.

Crystal structure

The crystal structure of anzaite-(Ce) characterizes in:[1]

  • the presence of layers with REE (square antiprismatic coordination) and Fe (octahedral)
  • the presence of layers with Ti with coordination numbers 5 and 6
  • disorder of Fe, VTi and two of four present anion sites

The disordered sites are located on the (010) planes, separated by ordered domains containing REE, VITi (octahedral) and two oxide-anion sites.[1]

References
  1. Chakhmouradian, A. R., Cooper, M. A., Medici, L., Abdu, Y. A., and Shelukhina, Y. S., 2015. Anzaite-(Ce), a new rare-earth mineral and structure type from the Afrikanda silicocarbonatite, Kola Peninsula, Russia. Mineralogical Magazine 79(5), 1231-1244
  2. "Anzaite-(Ce): Anzaite-(Ce) mineral information and data". Mindat.org. Retrieved 2016-03-04.
  3. "Lucasite-(Ce): Lucasite-(Ce) mineral information and data". Mindat.org. Retrieved 2016-03-10.


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