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Liandratite mineral

Hexavalent uranium niobate-tantalate mineral with current September 2026 IMA-CNMNC approved end-member formula U6+Nb2O8 (natural solid-solution formula U6+(Nb,Ta)2O8 with Nb:Ta ~ 5:1), status A, and approval number IMA 1975-039. Mucke and Strunz (1978) described the type material from the giant-grained beryl-columbite-petscheckite zone B of the Antsakoa I granitic pegmatite near Berere, ~40 km northeast of Tsaratanana, Madagascar, where liandratite forms 1-2 mm yellow to yellow-brown glassy, conchoidally fracturing metamict crusts epitaxially coating oxidized petscheckite (U4+Fe2+(Nb,Ta)2O8) crystals embedded in quartz. Cameca MS-46 electron-microprobe and microchemical analysis (Table 2, p. 944) yielded ~50 wt% UO2 (present in the hexavalent U6+ oxidation state, corresponding to 48.73 wt% UO3 in the theoretical Nb:Ta = 5:1 formula), ~50 wt% combined Nb2O5 + Ta2O5 with atomic ratio Nb:Ta ~ 5:1 (theoretical Nb2O5 36.22, Ta2O5 15.05 wt%), ~0.5 wt% H2O, and trace Fe, Mn, Th, and Pb. Unheated natural liandratite is completely X-ray amorphous (metamict) with isotropic refractive index n = 1.83, reflectance ~8.6% in air, Mohs hardness ~3.5, and measured density ~6.8 g/cm3. Heating metamict liandratite at red heat (~650 degrees C) and for 24 hours at 1000 degrees C recrystallized it as a single trigonal/hexagonal phase in space group P-31m (D3d^1) with a = 6.36, c = 4.01 A, c/a = 0.6305, Z = 1, Dmeas = 7.0 g/cm3, and Dcalc = 7.11 g/cm3 (for Nb:Ta = 5:1; Dcalc = 6.80 g/cm3 for pure UNb2O8 and 9.01 g/cm3 for UTa2O8), isostructural with synthetic hexagonal UTa2O8. Distinct from petscheckite (U4+Fe2+(Nb,Ta)2O8), oxyuranobetafite, samarskite-(Y), and elemental uranium, niobium, or tantalum; no criticality designation, microbial mechanism, or industrial recovery yield is asserted.

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Identifiers & Classification

System Identifier Label
IMA IMA:1975-039 Liandratite

Microbial & Biochemical Mechanisms (1)

Liandratite other Laboratory thermal annealing and trigo

Laboratory thermal annealing and trigonal P-31m recrystallization of metamict liandratite

other

Annealing X-ray-amorphous (metamict) natural liandratite from the Antsakoa I pegmatite at red heat (~650 degrees C) and for 24 hours at 1000 degrees C restored a sharp single-phase trigonal/hexagonal P-31m diffraction pattern (a = 6.36, c = 4.01 A, Z = 1, isostructural with synthetic hexagonal U6+Ta2O8) and increased measured density from ~6.8 to 7.0 g/cm3 without decomposition into cubic uranpyrochlore or extraneous oxide phases; in addition, prolonged oxidizing heating of coexisting metamict petscheckite at 1000 degrees C oxidized and converted its U4+ component into the same trigonal liandratite phase alongside minor FeNbO4.

Experimental Context & Analytical Limits:
Laboratory heating and X-ray diffraction experiments reported by Mucke and Strunz (1978), Tables 3-5 and pp. 944-946, establishing the structural identity of liandratite and its oxidative genetic link to petscheckite.
Curated Evidence Points:
Pages 944-945 and Tables 3 and 5 demonstrate that metamict liandratite (Dmeas ~ 6.8 g/cm3) recrystallizes at red heat (~650 degrees C) and 1000 degrees C (24 h) into a single trigonal P-31m phase (a = 6.36, c = 4.01 A, Z = 1, Dmeas = 7.0 g/cm3) with a powder pattern identical to synthetic hexagonal UTa2O8.
Because natural unheated liandratite is completely metamict, all unit-cell parameters and single-crystal Weissenberg/Debye-Scherrer data in Tables 3 and 5 represent thermally annealed material rather than unheated natural crystals.

Sources & References

  1. ima_2026_09: IMA-CNMNC, The New IMA List of Minerals, September 2026, PDF page 125, Liandratite row: formula U6+Nb2O8, status A, IMA No. 1975-039, country Madagascar, reference American Mineralogist 63 (1978), 941; column definitions on PDF page 1.
    https://cnmnc.units.it/files/editor/IMA_Master_List_(2026-09).pdf (accessed 2026-10-23)
  2. mucke_1978_liandratite: Mucke A, Strunz H (1978), Petscheckite and liandratite, two new pegmatite minerals from Madagascar, American Mineralogist 63:941-946. Complete 6-page primary PDF visually inspected: Antsakoa I pegmatite occurrence and epitaxial alteration sequence from petscheckite pp. 941-944; Cameca MS-46 microchemical analysis Table 2 p. 944; thermal recrystallization at 650-1000 C and trigonal P-31m X-ray diffraction Tables 3 and 5 pp. 944-946.
    https://www.rruff.net/doclib/am/vol63/AM63_941.pdf (accessed 2026-10-23)

Curation History

Timestamp Curator Action Summary
2026-10-23T07:15:00Z antigravity CREATE Created liandratite mineral record with verified IMA:1975-039 identity, Antsakoa I pegmatite microprobe chemistry, trigonal P-31m crystallography, and bounded laboratory metamict thermal recrystallization mechanism from the complete 1978 primary study.

Record source: data/records/liandratite.yaml