CMMMech > Mineral > Coconinoite

Coconinoite mineral

Coconinoite (IMA 1965-003) is an IMA-accepted hydrated iron-aluminum uranyl phosphate-sulfate mineral with IMA September 2026 Master List formula Fe3+2Al2(UO2)2(PO4)4(SO4)(OH)2·20H2O. Described by Young, Weeks, and Meyrowitz (1966) from the oxidized zone of Colorado Plateau uranium deposits at the Sun Valley mine (Coconino County, Arizona, USA), Blackwater No. 4 and Huskon No. 7 mines (Apache County, Arizona, USA), and the Jomac mine (White Canyon district, San Juan County, Utah, USA), where it forms light creamy-yellow microcrystalline aggregates of lath-shaped grains (6 x 2 um) in seams with gypsum, jarosite, limonite, quartz, clay, and coalified wood. Microchemical analyses in Table 2 (p. 656) report for Blackwater No. 4 sample 1715 Fe2O3 9.7, Al2O3 6.6, UO3 34.9, P2O5 18.3, SO3 5.4, H2O- 18.2, H2O+ 5.8 (total H2O 24.0), CaO 0.1, CO2 < 0.1, Na2O < 0.1, acid-insol. 0.5, total 99.5 wt%, and for Jomac sample T-J2-53 Fe2O3 10.3, Al2O3 6.5, UO3 34.2, P2O5 17.7, SO3 6.1, total H2O 23.4, CaO < 0.1, CO2 0.7, Na2O 0.1, acid-insol. 1.0, total 100.0 wt%. Possibly monoclinic, with strongest X-ray powder diffraction lines at 11.05(100), 5.52(42), and 5.61(18) Å, SGmeas = 2.70, Dcalc = 2.68 g/cm3, nonfluorescent under ultraviolet light, and unheated biaxial (–) optics with alpha = 1.550(5), beta = 1.586(5), gamma = 1.590(5), and 2V = 28–43° (average 40°).

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Identifiers & Classification

System	Identifier	Label
IMA	`IMA:1965-003`	Coconinoite

Microbial & Biochemical Mechanisms (1)

Abiotic thermal dehydration, basal spacing contraction, and TGA/DTA desulfation of coconinoite

other

Low-temperature dehydration of coconinoite at 135–215 °C with contraction of its basal X-ray spacing from 11.05 Å to 8.49–8.18 Å and elevation of refractive indices (measured on sample EVC-6 after the reversible 2.5 h treatment at 135 °C: alpha = 1.605(5), calculated beta = 1.630, gamma = 1.645(5), 2V = 75 ± 5°), followed in Chevenard thermogravimetric analysis (514 mg of sample 1715 heated 22–982 °C) and Eberhard DTA by complete dehydration (23.7 wt% water-associated loss through 450 °C; double endotherm at 150–250 °C) and high-temperature sulfur-oxide-associated mass loss (5.3 wt% between 600 and 850 °C; endotherm near 800 °C, described as SO2 loss on p. 655 and SO3 loss on p. 657; step losses sum to 29.0 wt% whereas Fig. 2 separately reports 28.7 wt% total loss by 982 °C).

Experimental Context & Analytical Limits:
Abiotic laboratory oven heating, Chevenard thermogravimetric analysis (TGA, 22–982 °C), and Eberhard differential thermal analysis (DTA); no microbial, enzymatic, or bioleaching mechanism was tested or reported in Young, Weeks, and Meyrowitz (1966).

Curated Evidence Points:

Support Source: young_1966_coconinoite

Oven heating of coconinoite sample EVC-6 at 135 °C for 2.5 hours reversibly dehydrates the mineral, raising refractive indices to alpha = 1.605(5), calculated beta = 1.630, gamma = 1.645(5) (2V = 75 ± 5°, Table 1, p. 655) and contracting the basal X-ray spacing from 11.05 Å to 8.49 Å (and to 8.30 Å at 174 °C and 8.18 Å at 215 °C), while Chevenard thermogravimetric analysis (22–982 °C on 514 mg of sample 1715) and Eberhard DTA record a 23.7 wt% water-associated loss through 450 °C (double endotherm at 150–250 °C; distinct from the 23.4 wt% chemical-analysis H2O total of Jomac sample T-J2-53) followed by a 5.3 wt% sulfur-oxide-associated mass loss from 600 to 850 °C (endotherm near 800 °C, referred to as SO2 on p. 655 and SO3 on p. 657; the two step losses sum to 29.0 wt%, whereas Fig. 2 separately states 28.7 wt% total loss by 982 °C, pp. 654–657, 663).

Sources & References

ima_2026_09: IMA-CNMNC (Pasero M., 2026), The New IMA List of Minerals – A Work in Progress (Updated: September 2026), PDF p. 48, Coconinoite row: status A, IMA 1965-003, formula Fe3+2Al2(UO2)2(PO4)4(SO4)(OH)2·20H2O, reference Young E.J., Weeks A.D., Meyrowitz R. (1966) American Mineralogist 51, 651-663.
https://cnmnc.units.it/files/editor/IMA_Master_List_(2026-09).pdf (accessed 2026-10-24)
young_1966_coconinoite: Young EJ, Weeks AD, and Meyrowitz R (1966), Coconinoite, a new uranium mineral from Utah and Arizona, American Mineralogist 51:651-663.
https://www.rruff.net/doclib/am/vol51/AM51_651.pdf (accessed 2026-10-24)

Curation History

Timestamp	Curator	Action	Summary
`2026-10-24T07:30:00Z`	antigravity	CREATE	Created mineral record for Coconinoite (IMA:1965-003) from the IMA September 2026 Master List and the primary type-description paper by Young, Weeks, and Meyrowitz (1966) in American Mineralogist 51:651-663, including its abiotic thermal dehydration and TGA/DTA desulfation mechanism.
`2026-10-24T10:45:00Z`	antigravity	EDIT	Resolved CMM120-F1 (issue #838) by aligning sample-labeled chemical analyses (1715 vs T-J2-53), EVC-6 dehydrated optical data (calculated beta = 1.630, 2V = 75 ± 5°), Chevenard TGA water loss (23.7 wt% on sample 1715), and high-temperature sulfur-oxide loss notes with Young, Weeks, and Meyrowitz (1966), and simplifying sources[1].title to a concise bibliographic citation.
`2026-10-24T11:27:00Z`	antigravity	EDIT	Applied reviewed conservative correction for CMM120-F1 (issue #838): corrected Table 2 locator to p. 656, unheated optical uncertainty to ±0.005 (Table 1, p. 655), and restricted reversible dehydration claim to the 135 °C 2.5 h EVC-6 experiment.

Record source: data/records/coconinoite.yaml