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CMMMech > Mineral > Caysichite-(Y)

Caysichite-(Y) mineral

A natural yttrium- and calcium-bearing silicate-carbonate mineral. The September 2026 IMA list retains (Ca,Yb,Er)4Y4(Si8O20)(CO3)6(OH)(H2O)5·2H2O and records a 1987 special-procedure renaming; that year is not an approval accession. The 1974 original described Evans-Lou mine material from Quebec, Canada, formerly labelled UN-11 and UN-16, with type material deposited as Geological Survey of Canada collection 10402. Most analyses used hand-picked colourless crusts; a separate yellow grain contained an interstitial Y-rich material and a rim tentatively identified as synchysite-(Y), so its chemistry is not pooled with the colourless material. The 1978 refinement on a specimen supplied by Hogarth established orthorhombic Ccm21 symmetry and double-crankshaft silicate chains. Its Y/Ca/REE site assignments and OH/water distribution were model-based; hydrogen atoms were not located. A 2025 study of separate Ploskaya Mountain, Russia, material supports a related structure but explicitly leaves its species equivalence to the Canadian material unresolved: proposed dominant cations differ between sites. It proposes vacancy and carbonate-protonation models, without locating hydrogen, and requests renewed study of the type locality material. Its proposed formula does not replace the current IMA formula here. Published numerical formula and reflection-count discrepancies are retained in the source dossier rather than silently reconciled. Geological formation by alteration of hellandite remains an interpretation from textures and associations, not a demonstrated microbial process. No criticality-list designation, extraction yield or industrial deployment is asserted.

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Microbial & Biochemical Mechanisms (1)

Caysichite-(Y) other Laboratory heating of natural Canadian

Laboratory heating of natural Canadian caysichite

other

Heating caused mass loss and an end product with an apatite-type diffraction pattern. Dehydration followed by two decarbonation stages was the original authors' interpretation, without evolved-gas identification or a chemically established final apatite species.

Experimental Context & Analytical Limits:
The 1974 study used four different hand-picked natural samples; this is not a reported set of four replicate TGA runs. Figure 3 specifies TGA in air at 12 degrees C per minute, ending at 1120 degrees C. Figure 4 instead specifies DTA in CO2 at 10 degrees C per minute. A separate static-heating sequence in air used 15 minutes at 350 degrees C, 15 minutes at 550 degrees C, and 50 minutes at 1100 degrees C. Thermal aliquot masses, quantified purity and analytical uncertainty were not supplied. These laboratory observations do not establish recovery of a rare-earth product or operating conditions for industrial treatment.
Curated Evidence Points:
The thermal section p.296 and Figure 3 report TGA losses of 8.3 percent over 290–580 degrees C, 10.6 percent over 580–895 degrees C and 5.3 percent over 895–1120 degrees C. The reported total is 24.3 percent, whereas the rounded stages sum to 24.2 percent; neither value is silently substituted. The body attributes an apatite-structure diffraction pattern and swelling without melting to the end product. Static-heating cumulative losses were 2.84, 9.37 and 24.85 percent at the three successive conditions; these are not separate extraction efficiencies or combined with the TGA series.
The assignments of the three TGA stages to water and then CO2 loss are expressly tentative in the body. Separate DTA peaks include 431 and 801 degrees C, with minor high-temperature events. The abstract calls the 1120-degree product a DTA product, whereas the thermal paragraph describes it with TGA; the exact product-arm attribution is therefore uncertain. No final-product chemical analysis, phase fraction, evolved-gas measurement, elemental balance or isolated REE recovery is reported.

Sources & References

  1. ima_2026_09: IMA-CNMNC, The New IMA List of Minerals, September 2026; definitions PDF page 1 and Caysichite-(Y) row page 39, renamed status Rn, 1987 special procedure.
    https://cnmnc.units.it/files/editor/IMA_Master_List_(2026-09).pdf (accessed 2026-10-16)
  2. hogarth1974: Hogarth DD, Chao GY, Plant AG and Steacy HR (1974), Caysichite, a new silico-carbonate of yttrium and calcium. Canadian Mineralogist 12:293–298. Full six-page original; specimen and type repository pp.293–294, chemistry Table 3 and pp.295–296, thermal experiments pp.296–297 and Figures 3–4, infrared Figure 5 and origin discussion p.297. TGA in air and DTA in CO2 are separate experiments.
    https://www.rruff.net/doclib/cm/vol12/CM12_293.pdf (accessed 2026-10-16)
  3. mellini1978: Mellini M and Merlino S (1978), Caysichite: A double crankshaft chain structure. Canadian Mineralogist 16:81–88. Full eight-page original; specimen and diffraction methods pp.81–83, Tables 1–5, Figures 1–5 and model-derived hydrogen scheme pp.86–87. Historical CISTI structure-factor deposit was not acquired; no independent re-refinement is claimed.
    https://www.rruff.net/doclib/cm/vol16/CM16_81.pdf (accessed 2026-10-16)
  4. krivovichev2025: Krivovichev SV, Yakovenchuk VN, Goychuk OF and Pakhomovsky YA (2025), Caysichite-(Y) from the Ploskaya Mountain (Kola Peninsula, Russia): Crystal-Structure Refinement and the Chemical Formula. Crystals 15:799, DOI 10.3390/cryst15090799. Full sixteen-page primary; methods pp.3–5, Tables 1–6, Figures 1–6, site-assignment qualifications pp.5,7–8, hydrogen limitations p.11 and unresolved species/formula discussion pp.12–13. The cited CSD 2482225 deposit was not acquired at curation; its contents are not independently verified by this record.
    https://pureportal.spbu.ru/files/141550754/2025_caysichite_Y.pdf (accessed 2026-10-16)

Curation History

Timestamp Curator Action Summary
2026-10-16T09:28:27.053352Z codex /root/round104_ree (GPT-6; codex) CREATE Added current mineral identity, original specimen characterization and qualified abiotic thermal evidence; retained later species and formula uncertainty.
2026-10-22T13:21:22Z claude (claude-opus-4-6; antigravity) EDIT Normalize IMA-CNMNC Master List source id from ima2026 to canonical ima_2026_09 (Issue #817).

Record source: data/records/caysichite-y.yaml