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Gaidonnayite mineral

Hydrated sodium-zirconium silicate mineral with current September 2026 IMA-CNMNC approved formula Na2ZrSi3O9(H2O)2, status A, and approval number IMA 1973-008. Chao and Watkinson (1974) described the cotype specimens (National Museum of Natural Sciences, Ottawa, T73/2-1 and T73/2-2) from nepheline syenite pegmatites at Mont Saint-Hilaire, Rouville County, Quebec, Canada, as an orthorhombic dimorph of catapleiite associated with hilairite, analcime, nenadkevichite, and epididymite. Electron-microprobe WDS analysis combined with thermogravimetric H2O determination (Table 3, p. 318) yielded SiO2 42.51, ZrO2 30.21, Nb2O5 3.00, TiO2 0.42, Na2O 13.11, K2O 2.20, H2O 9.25, total 100.70 wt%, corresponding on the basis of 9 anhydrous O atoms to the empirical formula (Na1.72K0.19)Sigma1.91(Zr1.00Nb0.09Ti0.02)Sigma1.11Si2.88O9·2.10H2O. Chao (1985) solved the crystal structure in acentric orthorhombic space group P21nb (a = 11.740(3), b = 12.820(3), c = 6.691(1) A, V = 1007.03 A3, Z = 4, R = 3.92%, Rw = 3.60% for 1211 observed reflections with I > 3sigma(I) out of 1280 unique reflections), demonstrating sinuous [Si3O9]n6n- chains along [101] cross-linked by isolated [ZrO6] octahedra and two distorted [NaO4(H2O)2] and [NaO3(H2O)3] octahedra. Donnay and Chao (1986) corrected a typographical error in Table 2 of Chao (1985) for the O(5) y coordinate (0.0149 rather than 0.1940, giving Si(2)-O(5) = 1.594(5) A instead of 2.660 A) and established double-donor hydrogen bonding of both H2O molecules OW(10) and OW(11). Distinct from catapleiite, georgechaoite (NaKZrSi3O9·2H2O), hilairite, and elemental zirconium; no criticality designation, microbial mechanism, or industrial recovery yield is asserted.

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Identifiers & Classification

System Identifier Label
IMA IMA:1973-008 Gaidonnayite

Microbial & Biochemical Mechanisms (1)

Gaidonnayite other Laboratory irreversible thermal dehydr

Laboratory irreversible thermal dehydration of gaidonnayite and transformation to wadeite-type Na2ZrSi3O9

other

Heating a 12.70 mg sample of natural Mont Saint-Hilaire gaidonnayite in air at 10 degrees C/min to 1000 degrees C produced a total dehydration mass loss of 9.25 wt% completed near 400 degrees C (resolved into two overlapping steps around 120-260 and 260-400 degrees C), with no water readsorption after standing in air at room temperature for 24 hours. Heating separate aliquots at 450 degrees C and 1000 degrees C converted the dehydrated mineral into a crystalline phase whose X-ray powder diffraction pattern closely resembled wadeite (K2ZrSi3O9) with smaller interplanar spacings corresponding to a sodium-wadeite analogue (Na2ZrSi3O9).

Experimental Context & Analytical Limits:
Thermogravimetric and thermal X-ray diffraction experiments in Chao and Watkinson (1974), pp. 318-319, heated 12.70 mg of hand-picked gaidonnayite in air at 10 degrees C/min from room temperature to 1000 degrees C, checked mass recovery after 24 h exposure to ambient air, and recorded X-ray powder diffraction patterns of aliquots heated to 450 and 1000 degrees C.
Curated Evidence Points:
Pages 318-319 report that the 12.70 mg sample lost 9.25 wt% H2O on heating to ~400 degrees C in two poorly resolved steps, showed zero weight gain after 24 hours at room temperature, and gave identical wadeite-like X-ray powder patterns after heating to 450 degrees C and 1000 degrees C.
Page 14 notes that the two crystallographically distinct water molecules OW(10) and OW(11) are each coordinated to two Na+ cations (Na1-OW10 = 2.411 A, Na2-OW10 = 2.660 A; Na1-OW11 = 2.416 A, Na2-OW11 = 2.382 A), explaining the two-stage dehydration and framework collapse into the anhydrous Na2ZrSi3O9 phase.

Sources & References

  1. ima_2026_09: IMA-CNMNC, The New IMA List of Minerals, September 2026, PDF page 79, Gaidonnayite row: formula Na2ZrSi3O9(H2O)2, status A, IMA No. 1973-008, country Canada, first reference Canadian Mineralogist 12 (1974), 316, second reference Canadian Mineralogist 23 (1985), 11; column definitions on PDF page 1.
    https://cnmnc.units.it/files/editor/IMA_Master_List_(2026-09).pdf (accessed 2026-10-22)
  2. chao_1974_gaidonnayite: Chao GY, Watkinson DH (1974), Gaidonnayite, Na2ZrSi3O9·2H2O, a new mineral from Mont St. Hilaire, Quebec, Canadian Mineralogist 12:316-319. Complete 4-page primary PDF visually inspected: occurrence, cotypes NMC T73/2-1 and T73/2-2, physical/optical and orthorhombic P21nb X-ray data Tables 1-2 pp. 316-318; WDS composition Table 3 and TGA dehydration/phase transformation pp. 318-319.
    https://www.rruff.net/doclib/cm/vol12/CM12_316.pdf (accessed 2026-10-22)
  3. chao_1985_gaidonnayite: Chao GY (1985), The crystal structure of gaidonnayite, Na2ZrSi3O9·2H2O, Canadian Mineralogist 23:11-15. Complete 5-page primary PDF visually inspected: single-crystal P21nb refinement Tables 1-4 and Figures 1-2 pp. 11-15.
    https://www.rruff.net/doclib/cm/vol23/CM23_11.pdf (accessed 2026-10-22)
  4. donnay_1986_gaidonnayite: Donnay G, Chao GY (1986), H2O molecules in gaidonnayite, Na2ZrSi3O9·2H2O: Specimen preservation and the role of hydrogen bonding, Canadian Mineralogist 24:417-419. Complete 3-page primary PDF visually inspected: correction of the O(5) y coordinate from 0.1940 to 0.0149 and bond-valence H-bonding analysis Tables 1-2 pp. 417-419.
    https://www.rruff.net/doclib/cm/vol24/CM24_417.pdf (accessed 2026-10-22)

Curation History

Timestamp Curator Action Summary
2026-10-22T07:20:00Z antigravity CREATE Created gaidonnayite mineral record with verified IMA:1973-008 identity, 1974 cotype WDS/TGA characterization and irreversible thermal dehydration/transformation mechanism, 1985 P21nb crystal-structure refinement, and 1986 O(5) coordinate correction.

Record source: data/records/gaidonnayite.yaml