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Pomite and pseudopomite, two new carbonate-encapsulating mixed-valence polyoxovanadate minerals

Kampf, Anthony R. and Hughes, John M. and Ma, Chi and Marty, Joe and Rose, Timothy P. (2022) Pomite and pseudopomite, two new carbonate-encapsulating mixed-valence polyoxovanadate minerals. American Mineralogist, 107 (11). pp. 2143-2149. ISSN 0003-004X. doi:10.2138/am-2022-8335. https://resolver.caltech.edu/CaltechAUTHORS:20221121-712406200.12

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Abstract

Pomite (IMA2021-063), ideally Ca₃[V⁴⁺₅V⁵⁺₁₀O₃₇(CO₃)]·37H₂O, and pseudopomite (IMA2021-064), ideally Ca₃.₅[V⁴⁺₆V⁵⁺₉O₃₇(CO₃)]·32H₂O, are two new polyoxometalate minerals from the Blue Streak mine, Bull Canyon, Montrose County, Colorado, U.S.A. Pomite properties: striated blades up to ~1 mm long; very dark green-blue color; green-blue streak; vitreous luster; brittle; Mohs hardness ≈2; irregular, splintery fracture; good cleavages on {010} and {001}; 2.19(2) g/cm⁻³ density; refractive indices in the vicinity of 1.70; weakly birefringent with little or no pleochroism. Pseudopomite properties: striated prisms and blades up to ~1 mm; very dark blue-green color; blue-green streak; vitreous luster; brittle; Mohs hardness ≈2; curved, irregular fracture; probably two fair cleavages, {100} and {001}; 2.40(2) g/cm⁻³ density; refractive indices in the vicinity of 1.72; no discernable birefringence or pleochroism. Electron microprobe analyses provided the empirical formulas Ca₃.₁₁[V⁴⁺₅.₂₃V⁵⁺₉.₇₇O₃₇(CO₃)]·37H₂O and Ca₃.₄₉[V⁴⁺₅.₉₈V⁵⁺₉.₀₂O₃₇(CO₃)]·29H₂O for pomite and pseudopomite, respectively. Pomite is triclinic, P1̅, with a = 12.3668(10), b = 12.9692(12), c = 22.068(2) Å, α = 99.038(7), β = 95.689(7), γ = 103.249(7)°, V = 3368.7(5) ų, and Z = 2. Pseudopomite is triclinic, P1̅, with a = 12.2910(18), b = 12.6205(15), c = 20.917(3) Å, α = 77.381(6), β = 85.965(5), γ = 64.367(7)°, V = 2853.6(7) ų, and Z = 2. The crystal structures of both minerals (pomite, R₁ = 0.103; pseudopomite, R₁ = 0.116) contain a novel [V⁴⁺ₓV⁵⁺₁₅₋ₓO₃₇(CO₃)]⁽¹⁺ˣ⁾⁻ heteropolyanion, which is unique in natural and synthetic materials but has similarities to the [V⁴⁺₈V⁵⁺₇O₃₆(CO₃)]⁷⁻ and [H₈V⁴⁺₁₅O₃₆(CO₃)]⁶⁻ heteropolyanions reported in synthetic phases.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.2138/am-2022-8335DOIArticle
http://www.minsocam.org/MSA/AmMin/TOC/2022/Nov2022_data/AM-22-118335.zipPublisherData
ORCID:
AuthorORCID
Kampf, Anthony R.0000-0001-8084-2563
Ma, Chi0000-0002-1828-7033
Additional Information:Reviewer Michael Schindler, two anonymous reviewers, and Associate Editor Diego Gatta are sincerely thanked for constructive comments, which improved the manuscript. This study was funded, in part, by the John Jago Trelawney Endowment to the Mineral Sciences Department of the Natural History Museum of Los Angeles County.
Funders:
Funding AgencyGrant Number
John Jago Trelawney EndowmentUNSPECIFIED
Issue or Number:11
DOI:10.2138/am-2022-8335
Record Number:CaltechAUTHORS:20221121-712406200.12
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20221121-712406200.12
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:117947
Collection:CaltechAUTHORS
Deposited By: Research Services Depository
Deposited On:01 Dec 2022 18:09
Last Modified:01 Dec 2022 18:09

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