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Franciscanite mineral

Franciscanite (IMA 1985-038) is an IMA-accepted manganese-vanadium nesosilicate mineral of the welinite group, the V5+ analogue of welinite, with IMA September 2026 Master List formula Mn2+6(V5+☐)(SiO4)2O3(OH)3 and empirical formula Mn5.96[V0.98[]1.02]Si2.00(O,OH)~14. Described by Dunn et al. (1986) from the Pennsylvania manganese mine in the Franciscan Complex, San Antonio Valley, Santa Clara County, California, USA (holotype NMNH 163041), where it occurs as dark brownish-red grains with gageite, sonolite, hausmannite, and barite. Electron microprobe analysis in Table 2 (p. 1523) gives SiO2 18.4, MnO 64.9, V2O5 13.5, Fe2O3 0.0, MgO 0.0, As2O5 0.0, and H2O 3.4 wt% (calculated from the Si:H ratio of type welinite because paucity of franciscanite precluded direct water/TGA measurement; thermal analyses in the paper were performed on welinite and impure örebroite), total 100.2 wt%. Hexagonal/trigonal (space group P3, inferred from possible P3 or P1), with a = 8.148(1) Å, c = 4.804(1) Å, V = 276.2 Å3, Z = 1, Dmeas = 4.1 g/cm3, Dcalc = 3.93 g/cm3, Mohs hardness 4, and uniaxial (+) optics with omega = 1.856(3) and epsilon = 1.882(3).

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Identifiers & Classification

System Identifier Label
IMA IMA:1985-038 Franciscanite

Sources & References

  1. ima_2026_09: IMA-CNMNC (Pasero M., 2026), The New IMA List of Minerals – A Work in Progress (Updated: September 2026), PDF p. 77, Franciscanite row: status A, IMA 1985-038, formula Mn2+6(V5+☐)(SiO4)2O3(OH)3, reference Dunn P.J. et al. (1986) American Mineralogist 71, 1522-1526.
    https://cnmnc.units.it/files/editor/IMA_Master_List_(2026-09).pdf (accessed 2026-10-24)
  2. dunn_1986_franciscanite: Dunn PJ, Peacor DR, Erd RC, and Ramik RA (1986), Franciscanite and örebroite, two new minerals from California and Sweden, related to redefined welinite, American Mineralogist 71:1522-1526.
    https://www.rruff.net/doclib/am/vol71/AM71_1522.pdf (accessed 2026-10-24)

Curation History

Timestamp Curator Action Summary
2026-10-24T07:30:00Z antigravity CREATE Created mineral record for Franciscanite (IMA:1985-038) from the IMA September 2026 Master List and the primary type-description paper by Dunn et al. (1986) in American Mineralogist 71:1522-1526.
2026-10-24T10:45:00Z antigravity EDIT Resolved CMM120-F9 (issue #838) by removing the unsupported franciscanite TGA claim, labeling Table 2 H2O = 3.4 wt% as calculated from the Si:H ratio of type welinite with exact Table 2 row labels (Fe2O3 0.0, As2O5 0.0), correcting space group P3 (inferred from possible P3 or P1), and simplifying sources[1].title to a concise bibliographic citation.

Record source: data/records/franciscanite.yaml