Cavansite mineral
Cavansite is a hydrated calcium vanadyl silicate mineral, Ca(V4+O)(Si4O10)(H2O)4, approved as IMA 1967-019 and retained in the September 2026 IMA list. It is a distinct species from pentagonite despite their related composition. The primary Oregon description and later natural-crystal work support a porous silicate framework containing vanadyl groups, calcium and water. Pcmn in the original description and Pnma in the 2012 study are different settings of the same orthorhombic space-group type, with the a and c axes interchanged. The 2009 proposed H3O+/OH-bearing formula is disputed by the 2012 hydrogen-bond refinement, and is not substituted for the current IMA formula. Natural-crystal heating experiments support protocol-dependent abiotic dehydration, without a microbial mechanism, mineral-specific recovery yield or industrial deployment. No criticality designation is inherited from vanadium or other constituents.
Microbial & Biochemical Mechanisms (1)
Abiotic dehydration and loss of crystalline order during heating
other
Danisi et al. (2012) followed one natural cavansite crystal by in situ single-crystal X-ray diffraction during heating in dry nitrogen. Refined water-site occupancies decreased and the framework contracted while remaining indexed in Pnma through 350 degrees C; crystalline order was lost at approximately 400 degrees C. The authors interpret successive changes in water positions and calcium coordination as dehydration. The recorded temperatures characterize this experiment, not universal thermodynamic transition points or an industrial recovery process.
Experimental Context & Analytical Limits:
A roughly 0.1 by 0.1 by 0.5 mm crystal from Wagholi quarry, Poona district, India, was mounted in an open 0.1 mm quartz-glass capillary and heated with a nitrogen blower. Complete diffraction data were collected at 25-degree increments up to 250 degrees C and 50-degree increments to 400 degrees C, holding at least 30 minutes at each next temperature before data collection. Water loss began in the refined model at 50 degrees C; approximate three-, two- and one-water descriptions were assigned at 75, 175 and 350 degrees C. The crystal broke between 150 and 175 degrees C, limiting subsequent integrated reflections; partly occupied water oxygens used constrained common isotropic displacement parameters. The same crystal followed through temperatures is not independent specimen replication. Water content here is inferred from a diffraction model, not a directly measured water or vanadium recovery mass balance.
A roughly 0.1 by 0.1 by 0.5 mm crystal from Wagholi quarry, Poona district, India, was mounted in an open 0.1 mm quartz-glass capillary and heated with a nitrogen blower. Complete diffraction data were collected at 25-degree increments up to 250 degrees C and 50-degree increments to 400 degrees C, holding at least 30 minutes at each next temperature before data collection. Water loss began in the refined model at 50 degrees C; approximate three-, two- and one-water descriptions were assigned at 75, 175 and 350 degrees C. The crystal broke between 150 and 175 degrees C, limiting subsequent integrated reflections; partly occupied water oxygens used constrained common isotropic displacement parameters. The same crystal followed through temperatures is not independent specimen replication. Water content here is inferred from a diffraction model, not a directly measured water or vanadium recovery mass balance.
Curated Evidence Points:
Support
Source:
danisi2012
Methods page 1875, Tables 1-2, discussion pages 1877-1880 and Figures 2-4 support condition-specific water-site changes, contraction and loss of crystalline order. The deposited tables and CIFs in the archive are part of the same measurement series. No organism, metal extraction assay or isolated product is reported for this experiment.
Partial
Source:
danisi2012
The abstract and simplified formulas describe complete loss of O9 water at 75 degrees C and O8 water at 350 degrees C, but Table 2b retains O9 occupancy 0.105(8) and Table 2d retains O8 occupancy 0.24(4); Figure 3d explicitly omits the residual O8 from the drawing. Thus three-, two- and one-water states are approximate model descriptions. Breakage, disorder and constrained refinement limit exact hydration assignments. Proposed removal of the last water as the cause of collapse is an interpretation. The printed high-temperature CIFs retain room-temperature diffraction metadata; experimental temperature attribution follows Table 1 and the described runs, not those uncorrected fields. No independent re-refinement was performed.
Partial
Source:
ishida2009
Independent powdered Wagholi samples were heated in air at 10 degrees C/min for TG-DTA and high-temperature powder diffraction (pages 242-246, Figures 1 and 4). Cavansite retained a diffraction pattern after cooling from 400 degrees C, while the text and Figure 4 describe an amorphous product at the higher heating stage. This differs from the dry-nitrogen single-crystal protocol and does not establish one transferable collapse temperature. The abstract says no intermediate amorphous phase; its scope is ambiguous alongside the terminal amorphous products described on pages 246 and 249, and it is not read as evidence that cavansite never becomes amorphous. The oxonium/hydroxyl interpretation is model-based because hydrogen positions could not be determined by the authors crystal refinement (page 244).
Refute
Source:
danisi2012
The claim refuted is that the 2009 H3O+/OH model is an established necessary structural formula for cavansite. Located hydrogen positions, bond-valence interpretation and geometric critique of proposed hydrogen bonds on pages 1876-1877 instead support water molecules for the studied crystal. This disagreement does not refute the observed abiotic dehydration or prove that all natural specimens have identical hydrogen configurations.
Partial
Source:
martucci2016_manuscript
The separate dynamic powder study used ground Wagholi crystals heated at 5 K/min in air and reports a different water-occupancy sequence, without resolving the split positions used by Danisi et al. The manuscript discusses time resolution, crystal dimensions, occupancy/displacement correlation and possible time-averaging as alternative explanations; it does not establish one model as universally correct. Its diffraction and thermal analyses are separate aliquots, and no controlled comparison isolates all protocol factors. The accessible version is an institutional preprint with prior referee criticism and author responses, not a checked final publisher version. Proposed applications of synthetic analogues are not demonstrated industrial deployment.
Sources & References
-
ima_2026_09: IMA-CNMNC. The New IMA List of Minerals, September 2026. Cavansite row, PDF page 38: Ca(V4+O)(Si4O10)(H2O)4, A, 1967-019; status definitions page 1.
https://cnmnc.units.it/files/editor/IMA_Master_List_(2026-09).pdf (accessed 2026-10-15) -
staples1973: Staples LW, Evans HT Jr, Lindsay JR (1973). Cavansite and pentagonite, new dimorphous calcium vanadium silicate minerals from Oregon. American Mineralogist 58:405-411. Original species description, locality and composition pages 405-407; natural association is not a controlled formation experiment.
https://msaweb.org/AmMin/AM58/AM58_405.pdf (accessed 2026-10-15) -
danisi2012: Danisi RM, Armbruster T, Lazic B (2012). In situ dehydration behavior of zeolite-like cavansite: A single-crystal X-ray study. American Mineralogist 97:1874-1880. Methods and Table 1 page 1875; experimental limitations and Table 2 page 1876; hydrogen-bond dispute and dehydration pages 1877-1879; Figures 1-4 and deposited Tables 3,5,6/CIFs.
https://doi.org/10.2138/am.2012.4228 (accessed 2026-10-15) -
danisi2012_archive: RRUFF archive of the Danisi et al. 2012 original and appended deposit AM-12-079, 43 PDF pages. Original pages 1-7; deposited displacement, distance and bond-valence tables pages 8-11, followed by four printed CIFs. Same study, not independent replication.
https://www.rruff.net/odr/view/downloadfile/80260 (accessed 2026-10-15) -
ishida2009: Ishida N, Kimata M, Nishida N, Hatta T, Shimizu M, Akasaka T (2009). Polymorphic relation between cavansite and pentagonite: Genetic implications of oxonium ion in cavansite. Journal of Mineralogical and Petrological Sciences 104:241-252. Methods pages 242-244; Figures 1,4,6; hydrogen-position limit page 244; amorphous-product discussion pages 246,249 and inferred hydrous-species model pages 248-250.
https://doi.org/10.2465/jmps.070724b (accessed 2026-10-15) -
martucci2016_manuscript: Martucci A, Rodeghero E, Cruciani G. Institutional manuscript ejm150060R1 associated with the 2016 publication Continuous dehydration of cavansite under dynamic conditions: an in situ synchrotron powder-diffraction study, European Journal of Mineralogy 28:5-13, DOI 10.1127/ejm/2015/0027-2512. Acquired 46-page preprint, not verified final publisher version: experimental sections PDF pages 15-17, differing water-site interpretation pages 21-23, Figures 1-9 and appended tables. Front matter includes referee objections and author responses; these are distinct from the revised manuscript.
https://iris.unife.it/retrieve/e309ade1-2f37-3969-e053-3a05fe0a2c94/ejm150060-1.pdf (accessed 2026-10-15)
Curation History
| Timestamp | Curator | Action | Summary |
|---|---|---|---|
2026-10-15T17:15:17.948403Z |
codex (GPT-6; codex) | CREATE | Created a cavansite mineral record with qualified single-crystal dehydration evidence, preserving residual water occupancy, specimen breakage, protocol dependence and disputed hydrogen assignments. |
2026-10-15T17:29:55.367000Z |
codex (GPT-6; codex) | EDIT | Addressed issue362 by qualifying the scope of Ishida2009 intermediate-phase wording while preserving terminal amorphization, measured outcomes and protocol distinctions. |
Record source: data/records/cavansite.yaml