CMMMech
CMMMech > Mineral > Kimuraite-(Y)

Kimuraite-(Y) mineral

Hydrated calcium-yttrium carbonate mineral with current September 2026 IMA-CNMNC approved formula CaY2(CO3)4·6H2O, status A, and approval number IMA 1984-073. Nagashima, Miyawaki, Takase, Nakai, Sakurai, Matsubara, Kato, and Iwano (1986) described the type specimens (deposited in the National Science Museum and the Sakurai Museum, Tokyo, Japan) from fissures in alkali olivine basalt (trachybasalt) at Kirigo, Hizen-cho, Higashi Matsuura-gun, Saga Prefecture, Kyushu, Japan, where it coexists with lanthanite-(Nd) and lokkaite-(Y) (CaY4(CO3)7·9H2O). Inductively coupled plasma atomic emission spectrometry (ICP-AES) for Ca and individual rare earths combined with gravimetric H2O (magnesium perchlorate absorption) and CO2 (soda-lime absorption) analysis (Table 1, p. 1029) yielded CaO 9.23, Y2O3 29.41, La2O3 0.50, Ce2O3 0.02, Pr2O3 0.37, Nd2O3 2.97, Sm2O3 0.95, Eu2O3 0.39, Gd2O3 2.49, Tb2O3 0.36, Dy2O3 2.44, Ho2O3 0.62, Er2O3 1.69, Tm2O3 0.17, Yb2O3 0.56, Lu2O3 0.06 (SigmaRE2O3 = 43.00 wt%, exhibiting a strong negative Ce anomaly attributed to oxidative Ce4+ fractionation during basaltic weathering), CO2 29.13, H2O 18.32, total 99.68 wt%, corresponding on the basis of 12 carbonate oxygens (O = 18 including water) to the empirical formula Ca0.99(Y1.57Nd0.11Gd0.08Dy0.08Er0.05Sm0.03Ho0.02Yb0.02La0.02Eu0.01Pr0.01Tb0.01Tm0.01)Sigma2.02(CO3)3.99·6.12H2O. Weissenberg, oscillation, and diffractometer powder X-ray diffraction (Table 3, p. 1031) established an orthorhombic body-centered unit cell (space group Imm2, Immm, I222, or I212121) with a = 9.2545(8), b = 23.976(4), c = 6.0433(7) A, V = 1340.9(3) A3, Z = 4, Dmeas = 2.6(1) g/cm3 (low due to flaky cleavage interspaces), and Dcalc = 2.98 g/cm3 (biaxial negative, alpha = 1.584(2), beta = 1.612(2), gamma = 1.626(2), 2V = 70(5) degrees, Mohs hardness ~2.5; dissolves with effervescence in dilute acids). Coupled DTA-TGA and heated-sample FTIR spectroscopy demonstrated two-stage thermal decomposition via dehydration at 60-400 degrees C and decarbonation at 400-750 degrees C. Distinct from lokkaite-(Y) (CaY4(CO3)7·9H2O), kamphaugite-(Y), tengerite-(Y), lanthanite-(Nd), and elemental yttrium or neodymium; no criticality designation, microbial mechanism, or industrial recovery yield is asserted.

Explore across X-Mech: MediaIngredientMech · CultureMech · CommunityMech · HabitatMech · TraitMech · CMMMech Network Graph

Identifiers & Classification

System Identifier Label
IMA IMA:1984-073 Kimuraite-(Y)

Microbial & Biochemical Mechanisms (1)

Kimuraite-(Y) other Laboratory two-stage thermal dehydrati

Laboratory two-stage thermal dehydration and decarbonation of natural kimuraite-(Y)

other

Simultaneous DTA-TGA heating of natural Kirigo kimuraite-(Y) from 60 to 1000 degrees C combined with FTIR spectra of aliquots heated at 300, 550, and 1000 degrees C demonstrated a two-stage thermal decomposition: (1) complete loss of crystallization water between 60 and 400 degrees C (marked by a strong DTA endotherm at 160 degrees C and the disappearance of the 3400 cm-1 O-H stretching and 1640 cm-1 H-O-H bending FTIR bands by 300 degrees C), followed by (2) multistep decarbonation of the anhydrous carbonate between 400 and 750 degrees C (four DTA endothermic peaks between 500 and 750 degrees C and progressive loss of the 1500/1400 cm-1 carbonate FTIR bands across 550-1000 degrees C) yielding rare-earth oxides plus residual trace CaCO3.

Experimental Context & Analytical Limits:
Thermal and spectroscopic experiments reported by Nagashima et al. (1986), pp. 1030-1031 and Figures 5-6, complemented by independent gravimetric determination of 18.32 wt% H2O and 29.13 wt% CO2 (47.45 wt% combined volatiles, matching the ~48% total TGA weight loss in Figure 5).
Curated Evidence Points:
Pages 1030-1031 and Figures 5-6 show that DTA-TGA records continuous dehydration from 60 to 400 degrees C (160 degrees C endotherm) and decarbonation from 400 to 750 degrees C (four endotherms between 500 and 750 degrees C), while FTIR spectra at 20, 300, 550, and 1000 degrees C confirm loss of H2O bands at 300 degrees C and conversion to rare-earth oxides at 550-1000 degrees C.
Figure 6 and p. 1031 note that weak carbonate absorption bands (assigned to trace residual CaCO3) persist in the FTIR spectrum at 550-1000 degrees C, and no single-crystal structure of the intermediate 300 degrees C anhydrous carbonate phase was obtained.

Sources & References

  1. ima_2026_09: IMA-CNMNC, The New IMA List of Minerals, September 2026, PDF page 113, Kimuraite-(Y) row: formula CaY2(CO3)4·6H2O, status A, IMA No. 1984-073, country Japan, reference American Mineralogist 71 (1986), 1028; column definitions on PDF page 1.
    https://cnmnc.units.it/files/editor/IMA_Master_List_(2026-09).pdf (accessed 2026-10-23)
  2. nagashima_1986_kimuraite: Nagashima K, Miyawaki R, Takase J, Nakai I, Sakurai K, Matsubara S, Kato A, Iwano S (1986), Kimuraite-(Y), CaY2(CO3)4·6H2O, a new mineral from fissures in an alkali olivine basalt from Saga Prefecture, Japan, and new data on lokkaite-(Y), American Mineralogist 71:1028-1033. Complete 6-page primary PDF visually inspected: Kirigo occurrence and physical/optical properties pp. 1028-1029; ICP-AES and gravimetric chemical analysis Table 1 pp. 1029-1030; DTA-TGA and heated-sample FTIR thermal decomposition Figures 5-6 pp. 1030-1031; orthorhombic XRD Table 3 pp. 1031-1032.
    https://www.rruff.net/doclib/am/vol71/AM71_1028.pdf (accessed 2026-10-23)

Curation History

Timestamp Curator Action Summary
2026-10-23T07:15:00Z antigravity CREATE Created kimuraite-(Y) mineral record with verified IMA:1984-073 identity, Kirigo ICP-AES + gravimetric chemistry, orthorhombic crystallography, and bounded laboratory DTA-TGA/FTIR thermal decomposition mechanism from the complete 1986 primary study.

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