CMMMech > Mineral > Cabalzarite

Cabalzarite mineral

Hydrated calcium-magnesium-aluminum arsenate mineral of the tsumcorite group with current September 2026 IMA-CNMNC approved end-member formula CaMg2(AsO4)2(H2O)2 (general structural formula Ca(Mg,Al,Fe3+)2(AsO4)2(H2O,OH)2), status A, and approval number IMA 1997-012. Brugger, Meisser, Schenk, Berlepsch, Bonin, Armbruster, and Nyfeler (2000) described the holotype (MGL73785, sample CABA11, Musee Cantonal de Geologie, Lausanne) and cotype (Naturhistorisches Museum, Basel) from retrograde Alpine metamorphic fractures crosscutting braunite-rhodonite-spessartine manganese ore at the abandoned Falotta mine, Oberhalbstein, Graubunden, Switzerland, associated with quartz, Tilasite, kemmlitzite, palygorskite, manganoan calcite, grischunite, sarkinite, brandite, and manganberzeliite. JEOL JXA-8600 WDS electron-microprobe analysis of structure crystal CABA11.5 (mean of 4 point analyses, Table 2, p. 1309; ranges from 92 analyses across 16 grains in parentheses) yielded As2O5 55.57 (50.96-56.14), Al2O3 9.84 (4.52-11.51), MgO 7.54 (5.71-8.88), Fe2O3 4.38 (<0.04-11.40), Mn2O3 0.55 (0.32-5.21), SrO 0.49 (0.03-0.94), CaO 13.64 (12.02-15.53), SiO2 0.05 (<0.05-1.87), H2Ocalc 7.11 (5.87-7.30), total 99.17 wt%, corresponding on the basis of 10 O atoms to the empirical formula (Ca1.00Sr0.02)Sigma1.02(Al0.80Mg0.77Fe3+0.23Mn3+0.03)Sigma1.83(AsO4)2(H2O1.26OH0.74)2 (with Mg-dominant zones in the 92-analysis suite having Mg/(Mg+Al+Fe+Mn) up to 0.49 and Mg > Al > Fe3+). High-resolution ESRF synchrotron powder XRD on CABA11 (Table 4, p. 1310: monoclinic, space group C2/m, a = 8.945(1), b = 6.156(1), c = 7.358(1) A, beta = 115.30(2) degrees, V = 366.3(1) A3, Z = 2) and single-crystal XRD refinements on CABA11.5 (a = 8.925(2), b = 6.143(1), c = 7.352(1) A, beta = 115.25(3) degrees, V = 364.6(1) A3, R1 = 1.80% for 436 reflections with Fo > 4sigma(Fo), Dcalc = 3.73 g/cm3) and CABA20 (a = 8.9284(5), b = 6.1314(5), c = 7.3439(6) A, beta = 115.494(7) degrees, V = 362.9(1) A3, R1 = 1.86% for 367 reflections; Dmeas = 3.89(3) g/cm3, VHN50 = 429 kg/mm2, Mohs hardness ~5) established rutile-like chains of edge-sharing M(2)(O,OH,H2O)6 octahedra linked by AsO4 tetrahedra into [M2(AsO4)2(OH,H2O)2]2- sheets parallel to (001) connected by [8]-coordinated Ca at M(1) and strong symmetrical O1-H...O1 hydrogen bonds. Thermogravimetric heating under dry N2 recorded a single ~6 wt% dehydration step between 640 and 700 degrees C. Distinct from lotharmeyerite, ferrilotharmeyerite, talmessite, and elemental magnesium or arsenic; no criticality designation, microbial mechanism, or industrial recovery yield is asserted.

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Identifiers & Classification

System	Identifier	Label
IMA	`IMA:1997-012`	Cabalzarite

Microbial & Biochemical Mechanisms (1)

Laboratory high-temperature single-step dehydration of natural cabalzarite

other

Heating 3.30 mg of powdered natural cabalzarite (sample CABA14, containing <= 1 vol% impurities) in an open gold crucible at 10 degrees C/min under dry nitrogen up to 900 degrees C produced a single-step mass loss of ~6 wt% between 640 and 700 degrees C, matching the stoichiometric 5.87-7.30 wt% H2O content calculated from electron-microprobe analyses for H2O/OH groups at the O1 site.

Experimental Context & Analytical Limits:
Thermogravimetric analysis in Brugger et al. (2000), p. 1309, used a Perkin Elmer TGS-2 thermobalance on 3.30 mg of CABA14 powder heated to 900 degrees C at 10 degrees C/min in dry N2. The anomalously high dehydration onset (640-700 degrees C) reflects very strong hydrogen bonding across the [O1-H...O1]3- configuration (O1-O1 distance 2.567-2.589 A). Post-heating phase identification of the anhydrous residue was not reported.

Curated Evidence Points:

Support Source: brugger_2000_cabalzarite

Page 1309 reports that 3.30 mg of CABA14 powder heated in an open gold crucible under dry N2 at 10 degrees C/min to 900 degrees C underwent a single-step ~6 wt% weight loss between 640 and 700 degrees C, in quantitative agreement with the 5.87-7.30 wt% H2O calculated from EMPA stoichiometry.

Partial Source: brugger_2000_cabalzarite

Because the ~6 wt% TGA mass loss carries a ~10% relative uncertainty on the small 3.30 mg charge, the exact H2O:OH ratio at O1 was fixed by charge balance in the EMPA recalculation rather than by gravimetric water determination alone.

Sources & References

ima_2026_09: IMA-CNMNC, The New IMA List of Minerals, September 2026, PDF page 33, Cabalzarite row: formula CaMg2(AsO4)2(H2O)2, status A, IMA No. 1997-012, country Switzerland, reference American Mineralogist 85 (2000), 1307; column definitions on PDF page 1.
https://cnmnc.units.it/files/editor/IMA_Master_List_(2026-09).pdf (accessed 2026-10-23)
brugger_2000_cabalzarite: Brugger J, Meisser N, Schenk K, Berlepsch P, Bonin M, Armbruster T, Nyfeler D (2000), Description and crystal structure of cabalzarite, Ca(Mg,Al,Fe)2(AsO4)2(H2O,OH)2, a new mineral of the tsumcorite group, American Mineralogist 85:1307-1314. Complete 8-page primary PDF visually inspected: Falotta Mn-deposit occurrence, holotype MGL73785, physical/optical properties, and TGA dehydration pp. 1307-1309; 92-point EMPA chemistry Table 2 p. 1309; ESRF synchrotron powder XRD Table 4 and monoclinic C2/m single-crystal refinements Tables 5-7 and Figures 3-8 pp. 1309-1313.
https://www.rruff.net/doclib/am/vol85/AM85_1307.pdf (accessed 2026-10-23)

Curation History

Timestamp	Curator	Action	Summary
`2026-10-23T07:15:00Z`	antigravity	CREATE	Created cabalzarite mineral record with verified IMA:1997-012 identity, Falotta holotype EMPA chemistry, monoclinic C2/m single-crystal/synchrotron structure, and bounded laboratory TGA dehydration mechanism from the complete 2000 primary study.

Record source: data/records/cabalzarite.yaml