Ferricopiapite mineral
Ferricopiapite is the triclinic ferric-iron member of the copiapite group, ideally Fe(III)2/3Fe(III)4(SO4)6(OH)2·20H2O. The September 2026 IMA list recognizes it as a grandfathered species, distinct from mixed-valence copiapite and other copiapite-group minerals. The accepted original demonstrates abiotic preparation and acid-solution calorimetry of a characterized synthetic sample with nonideal composition and a minor unidentified impurity. It supplies no microbial synthesis or metal-recovery yield.
Microbial & Biochemical Mechanisms (2)
Ferricopiapite crystallization from hydrated ferric sulfate
other
A ferric sulfate solution produced yellow ferricopiapite in a sealed capsule at 323 K. Conventional and synchrotron powder diffraction, refinement and chemical analysis support the product assignment, with a detected minor impurity and nonideal composition retained.
Experimental Context & Analytical Limits:
Majzlan et al., Materials and methods, printed page 176 (PDF page 2): 2.5 g of the first supplier batch of hydrated ferric sulfate was mixed with 1.17 mL deionized water and dissolved in an ultrasonic bath for about 30 min. This starting batch was X-ray amorphous and contained approximately 21% water. The solution was sealed in a silica-glass capsule at 323 K. Precipitate appeared after 2 days and grew over the following 7 days; it was then ethanol-washed and dried at room temperature by reduced-pressure filtration. No inoculum, isolated-product yield or synthesis replicate count is reported.
Majzlan et al., Materials and methods, printed page 176 (PDF page 2): 2.5 g of the first supplier batch of hydrated ferric sulfate was mixed with 1.17 mL deionized water and dissolved in an ultrasonic bath for about 30 min. This starting batch was X-ray amorphous and contained approximately 21% water. The solution was sealed in a silica-glass capsule at 323 K. Precipitate appeared after 2 days and grew over the following 7 days; it was then ethanol-washed and dried at room temperature by reduced-pressure filtration. No inoculum, isolated-product yield or synthesis replicate count is reported.
Curated Evidence Points:
Support
Source:
majzlan2006
Materials and methods, printed page 176 (PDF page 2), gives the preparation. Table 1, printed page 177 (PDF page 3), and Table 3, printed page 178 (PDF page 4), report the ferricopiapite P-1 refinement. Table 5, printed page 179 (PDF page 5), gives fit statistics. This is a characterized synthetic preparation, not an experiment showing biological necessity or mineral recovery from waste.
Partial
Source:
majzlan2006
Results, printed pages 180-181 (PDF pages 6-7), reports an unidentified synchrotron diffraction peak at d = 10.570 angstrom, despite no impurity peaks in conventional XRD. The authors' estimate of at most 1% impurity is explicitly crude; it is not a validated product-purity measurement. Table 3 gives Fe1 occupancy 0.619(4), while Table 8 derives the bulk formula Fe4.78(SO4)6(OH)2.34(H2O)20.71. These sample-specific results are not identical to the ideal mineral formula.
Partial
Source:
majzlan2006
Materials and methods, printed page 176 (PDF page 2), distinguishes a second supplier batch with about 28% water, a copiapite-group phase and minor kornelite. Not all syntheses succeeded with that batch. The proposed grain-size and dissolution explanation is not tested as an isolated cause. Supplier naming alone therefore does not establish equivalent feed identity or reproducibility.
Sample-specific dissolution in an acid calorimetric cycle
other
The synthetic ferricopiapite sample was dissolved in an acid-solution calorimetric cycle at 298.15 K. The measured heat constrains its thermochemistry; it does not measure iron extraction efficiency, dissolution rate or isolated-product recovery.
Experimental Context & Analytical Limits:
Methods, printed page 179 (PDF page 5), uses an IMC-4400 calorimeter with 25 mL of standardized 5 N HCl. Sample pellets across the studied materials weighed 12-18 mg, with mass chosen for the thermochemical stoichiometry. In the relevant cycle, MgO was dissolved first and the ferric sulfate sample subsequently added to the same solvent. The experiment is therefore not a stand-alone assay in an unchanged fresh acid solution. Samples were kept at 295 K and 55% relative humidity; daily XRD and weight-loss checks found no changes during the experiments, whose overall storage duration is unspecified.
Methods, printed page 179 (PDF page 5), uses an IMC-4400 calorimeter with 25 mL of standardized 5 N HCl. Sample pellets across the studied materials weighed 12-18 mg, with mass chosen for the thermochemical stoichiometry. In the relevant cycle, MgO was dissolved first and the ferric sulfate sample subsequently added to the same solvent. The experiment is therefore not a stand-alone assay in an unchanged fresh acid solution. Samples were kept at 295 K and 55% relative humidity; daily XRD and weight-loss checks found no changes during the experiments, whose overall storage duration is unspecified.
Curated Evidence Points:
Support
Source:
majzlan2006
Thermochemistry, printed page 182 (PDF page 8), Table 10 on that page and Table 11, printed page 183 (PDF page 9), identify the dissolution cycle and report delta H8 = +74.20 ± 0.22 kJ/mol from five measurements. The uncertainty is two standard deviations of the mean. The molar basis is the analyzed Table 8 sample formula Fe4.78(SO4)6(OH)2.34(H2O)20.71, not one mole of iron or an assumed ideal endmember. Calorimetric replication does not establish independent synthesis replication.
Partial
Source:
majzlan2006
Discussion, printed pages 184-185 (PDF pages 10-11), and Figure 1 construct thermodynamic stability fields using estimated entropies, calculated Gibbs energies and specified activities. The ferricopiapite- rhomboclase boundary depends on sulfate versus bisulfate assumptions; the authors explicitly describe the plotted boundary as metastable. These calculations are not measured environmental pH thresholds, microbial transformation experiments or industrial performance data.
Sources & References
-
ima_2026_09: IMA-CNMNC. The New IMA List of Minerals, September 2026; Ferricopiapite row on PDF page 68 and definitions on pages 1-2. Formula Fe3+0.67Fe3+4(SO4)6(OH)2(H2O)14·6H2O; status G, original-description year 1939, not an IMA approval number.
https://cnmnc.units.it/files/editor/IMA_Master_List_(2026-09).pdf (accessed 2026-10-15) -
handbook: Handbook of Mineralogy. Ferricopiapite, version 1 (2001-2005), complete one-page entry; triclinic P-1, ferric copiapite-group member.
https://handbookofmineralogy.org/pdfs/ferricopiapite.pdf (accessed 2026-10-15) -
majzlan2006: Majzlan, J., Navrotsky, A., McCleskey, R. B. and Alpers, C. N. (2006). Thermodynamic properties and crystal structure refinement of ferricopiapite, coquimbite, rhomboclase, and Fe2(SO4)3(H2O)5. European Journal of Mineralogy 18(2), 175-186. DOI 10.1127/0935-1221/2006/0018-0175. Complete 12-page original, Tables 1-14 and Figure 1 inspected.
https://doi.org/10.1127/0935-1221/2006/0018-0175 (accessed 2026-10-15)
Curation History
| Timestamp | Curator | Action | Summary |
|---|---|---|---|
2026-10-15T13:54:49Z |
codex (GPT-6; codex) | CREATE | Created ferricopiapite from current mineral authorities and the complete synthesis and calorimetry original, retaining nonideal composition, impurity, feed-batch dependence and abiotic assay limitations. |
Record source: data/records/ferricopiapite.yaml