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Kozoite-(La) mineral

Kozoite-(La) is the lanthanum-dominant orthorhombic rare-earth hydroxyl carbonate mineral with ideal formula La(CO3)(OH), approved as IMA 2002-054. It is distinct from elemental lanthanum, other kozoite species, hydroxylbastnäsite-(La) and commercial rare-earth feeds. The original Mitsukoshi, Japan material consists of minute crystals in spherical aggregates with concentric La-dominant and Nd-dominant zones. Four La-domain microprobe analyses have average La0.83 and Nd0.40 on a two-cation basis, with appreciable Ca0.43; this is not a chemically pure La end member. Carbon and hydrogen could not be measured in that intergrown material: the reported carbonate, hydroxyl and water contents were calculated from an ancylite-type formula, while infrared bands support carbonate and OH. The analytical total including calculated volatiles is 101.19 wt%. Powder diffraction gives Pmcn and a = 4.986(4), b = 8.513(6), c = 7.227(10) Å; no single-crystal analysis was possible. Nearly matching diffraction patterns of the La and Nd species require chemical discrimination. The mechanism below concerns separately synthesized La carbonate, not dissolution of the natural zoned specimen. These sources do not establish microbial causality, industrial deployment or a jurisdiction-specific criticality designation.

Identifiers & Classification

System Identifier Label
IMA IMA:2002-054 Kozoite-(La)

Microbial & Biochemical Mechanisms (1)

Abiotic formation of synthetic La kozoite during carbonate aging

other

In a laboratory La-carbonate suspension aged at 35 °C, powder X-ray diffraction identified increasing kozoite alongside decreasing lanthanite. Table 1 and Figure 1b agree on 18 wt% kozoite and 82 wt% lanthanite at 24 h, 54 wt% kozoite and 46 wt% lanthanite at 192 h, and 100 wt% kozoite among the quantified crystalline phases at 360 h. These are fitted crystalline phase fractions, not a La mass balance, isolated-metal yield or recovery efficiency. Microscopy at 24 h shows La-kozoite spherulites on lanthanite surfaces. Dissolution-recrystallization and spherulitic growth are the authors' interpretation of the phase and morphology changes, rather than a directly resolved molecular pathway.

Experimental Context & Analytical Limits:
Terribili et al. (2025) mixed 40 mL of 50 mM Na2CO3 with 40 mL of 50 mM La-bearing solution prepared from La(NO3)3·6H2O and Milli-Q water. Solutions were brought to 35 °C before mixing; sealed glass reactors were held static in a preheated oven. Periodic 5 mL suspensions were vacuum-filtered through 0.2 µm polycarbonate filters, rinsed with isopropanol and air-dried. Cu Kα powder diffraction with database pattern identification and TOPAS Rietveld refinement supplied crystalline phase fractions; amorphous material is not quantified by these values. The time series and separate temperature arms supply phase comparators. Two replica experiments are described only for the ambient-temperature arm; independent replication and phase-fraction uncertainties are not specified for this 35 °C arm. The solution speciation discussion uses Nd-phase solubility constants because La-kozoite data were unavailable, so it is not a direct La-specific saturation measurement. Other temperature arms are not pooled with this experiment; the separate 80 °C, 72 h values differ between Table 1 (93 wt% kozoite, 7 wt% tengerite) and Figure 1d (94 wt% kozoite, 6 wt% tengerite), so that endpoint is not used. No microorganisms, natural ore feed or industrial-scale operation were tested in this arm.
Curated Evidence Points:
Methods page 946 defines the solution synthesis and phase analysis; Table 1 page 947 and Figure 1b page 948 agree on the three reported 35 °C phase fractions. Figure 8b page 955 shows La-kozoite on lanthanite after 24 h at 35 °C. Discussion pages 957-959 proposes the dissolution-recrystallization explanation and describes the substituted Nd thermodynamic data. The narrower laboratory phase-formation observation is supported; molecular causality, metal recovery and quantitative claims for the conflicting 80 °C endpoint remain unestablished.

Sources & References

  1. ima_2026_09: IMA-CNMNC. The New IMA List of Minerals, September 2026. Definitions PDF page 1 and Kozoite-(La) row page 116: La(CO3)(OH), A, 2002-054, Japan. Official homepage and downloaded authority list checked 16 October 2026.
    https://cnmnc.units.it/files/editor/IMA_Master_List_(2026-09).pdf (accessed 2026-10-16)
  2. miyawaki2003: Miyawaki R, Matsubara S, Yokoyama K, Iwano S, Hamasaki K and Yukinori I (2003). Kozoite-(La), La(CO3)(OH), a new mineral from Mitsukoshi, Hizen-cho, Saga Prefecture, Japan. Journal of Mineralogical and Petrological Sciences 98:137-141. DOI 10.2465/jmps.98.137. Complete five-page original scan, Figures 1-4 and Tables 1-2 visually inspected. Chemistry and calculated volatiles pages 138-139; diffraction pages 138-140. J-STAGE confirms 2003 publication separately from 2004 online release and lists zero supplementary materials.
    https://doi.org/10.2465/jmps.98.137 (accessed 2026-10-16)
  3. terribili2025: Terribili L, Szucs AM, Maddin M, Zubovic KP, Rateau R and Rodriguez-Blanco JD (2025). Mechanistic Insights into the Early-Stage Crystallization and Nanophase Formation of Metastable Light Rare-Earth Carbonates. Crystal Growth & Design 25:945-962. DOI 10.1021/acs.cgd.4c01168. Complete article and eight-page Supporting Information 10.1021/acs.cgd.4c01168.s001 accessible; relevant Methods pages 946-948, Table 1, Figures 1 and 8, and discussion pages 957-959 re-inspected with all SI pages. The curated 35 °C solution-aging arm is separate from the La dry-heating/rehydration experiment in the lanthanite-(La) record.
    https://doi.org/10.1021/acs.cgd.4c01168 (accessed 2026-10-16)

Curation History

Timestamp Curator Action Summary
2026-10-16T02:42:30.559284Z codex (GPT-6; codex) CREATE Added verified mineral identity and bounded abiotic transformation evidence, preserving natural/synthetic boundaries, measured versus calculated values, source discrepancies and missing experimental details.

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