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Monazite-(La) mineral

Monazite-(La) is the lanthanum-dominant anhydrous phosphate mineral with ideal formula La(PO4), distinct from monazite-(Ce), the monazite group, hydrated rhabdophane-(La), elemental lanthanum and mixed monazite ores. The September 2026 IMA list records renamed status and a 1966 special procedure, not a numbered approval accession. Ni et al. (1995) resolved a synthetic LaPO4 crystal in monoclinic P21/n monazite with nine-coordinate rare-earth sites. Their natural monazite comparator was Ce-dominant, not natural monazite-(La). Zhoujin et al. (2025) separately produced synthetic La monazite by abiotic microwave-assisted hydrothermal treatment. Characterization of synthetic analogues does not demonstrate microbial formation, recovery from an ore or waste, or industrial operation. Criticality is not inherited from the lanthanum constituent.

Microbial & Biochemical Mechanisms (1)

Abiotic microwave-assisted formation of synthetic La monazite

other

Synthetic La rhabdophane was treated in 1 M phosphoric acid at 210 degrees C for one hour using microwave-assisted hydrothermal heating, producing a powder assigned to monazite by X-ray diffraction. Separate reagent routes using LaCl3 or LaF3 at 230 degrees C for one hour also produced source-assigned monazite powders. These are laboratory preparation and mineral transformation experiments; neither an isolated-lanthanum recovery yield nor performance with real nuclear waste was measured.

Experimental Context & Analytical Limits:
The series used a CEM Discover 2.0 instrument, an infrared temperature sensor, stirring and 35-mL Pyrex tubes. The initial La oxide reagent was supplied as 99.9% La2O3. The rhabdophane preparation used 8 mL of 1 M H3PO4 at 100 degrees C for 30 minutes; the subsequent monazite preparation used 210 degrees C for one hour. The methods also describe direct monazite preparation from starting reagents, but Figure 4B specifically labels the precursor-conversion series. Figure S7 shows the separate LaCl3 and LaF3 routes, whose methods specify 8 mL of 1 M H3PO4 and 230 degrees C for one hour. Products were filtered and washed with water and acetone. PXRD used Cu Kalpha radiation over 5-65 degrees 2theta. La starting amounts, independent replicate counts and quantitative La phase-purity or product yields are not specified. The diffraction assignment does not prove complete purity below analytical detection. No matched La acid-free, conventionally heated or pH-series comparison is reported in the acquired source. The detailed proton-assisted pathway, low-temperature onset and chemical-durability tests concern Nd material and are not transferred to La.
Curated Evidence Points:
The La-labeled powder trace in Figure 4B and its caption support conversion of synthetic La rhabdophane in 1 M H3PO4 at 210 degrees C for one hour. Figure S2 identifies the La precursor preparation; Figure S7 and the microwave methods independently identify the two starting-salt routes at 230 degrees C. These are distinct arms of one study, not independent replications.
Methods do not give a La-specific starting mass or a mass-balanced yield. The 100-mg loading, HCl pH series and fitted phase fractions belong to Nd rhabdophane. Supplement Table S4 lists pH 0.83 where Figure S11 says 0.65, and Figures S18-S20 repeat a 6.38 caption despite different patterns; these unresolved labels are not used to construct a La pH response. The study's in-situ Nd observations and proposed proton pathway are not direct proof of a La molecular mechanism. Chemical durability of Nd powder does not establish La or transuranic waste-form performance.

Sources & References

  1. ima_2026_09: IMA-CNMNC. The New IMA List of Minerals, September 2026. PDF page 146 Monazite-(La): La(PO4), Rn, 1966 s.p., Kazakhstan. Status definitions pages 1-2; renamed status and special-procedure year do not provide a numbered mineral approval identifier.
    https://cnmnc.units.it/files/editor/IMA_Master_List_(2026-09).pdf (accessed 2026-10-15)
  2. ni1995: Ni Y, Hughes JM and Mariano AN (1995). Crystal chemistry of the monazite and xenotime structures. American Mineralogist 80:21-26. DOI 10.2138/am-1995-1-203. Complete original; synthetic crystal provenance and diffraction methods pages 22-23; Table 1 La(PO4) column is separate from the natural Ce-dominant monazite column; structure discussion pages 23-26. Deposited Tables 4-5 were not inspected and no deposited refinement or reflection values are imported.
    https://www.msaweb.org/MSA/AmMin/TOC/Articles_Free/1995/Ni_p21-26_95.pdf (accessed 2026-10-15)
  3. zhoujin2025: Zhoujin Y, Tisdale HB, Keerthisinghe N, Morrison G, Smith MD, Hadermann J, Besmann TM, Amoroso J and zur Loye HC (2025). A low-temperature, one-step synthesis for monazite can transform monazite into a readily usable advanced nuclear waste form. Science Advances 11:eadt3518. DOI 10.1126/sciadv.adt3518. Complete original XML, original figures and supplementary Tables S1-S11/Figures S1-S29 acquired. La-specific evidence: Figure 4B, Figure S2, Figure S7 and Materials and Methods, Reagents/Microwave-assisted reaction/Powder XRD. The detailed pH, time, in-situ transition and durability studies use NdPO4.
    https://doi.org/10.1126/sciadv.adt3518 (accessed 2026-10-15)

Curation History

Timestamp Curator Action Summary
2026-10-15T22:12:58Z codex (GPT-6; codex) CREATE Added distinct La monazite identity and primary-supported synthetic microwave preparation, separating precursor and salt routes and excluding Nd-only results and unverified microbial leads.

Record source: data/records/monazite-la.yaml