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Edwindavisite, Cu(C2O4)(NH3), a new oxalate mineral, from the Rowley mine, Maricopa County, Arizona, USA

Published online by Cambridge University Press:  27 February 2025

Hexiong Yang Open the ORCID record for Hexiong Yang [Opens in a new window] ,
Xiangping Gu Open the ORCID record for Xiangping Gu [Opens in a new window] ,
Anthony R. Kampf Open the ORCID record for Anthony R. Kampf [Opens in a new window] ,
Joe Marty ,
Ronald B. Gibbs  and
Robert T. Downs
Hexiong Yang*
Affiliation:
Department of Geosciences, University of Arizona, Tucson, AZ, USA
Xiangping Gu
Affiliation:
Guanghua School of Gems and Art Design, Jiangxi Institute of Applied Science and Technology, Nanchang, JX, China
Anthony R. Kampf
Affiliation:
Mineral Sciences Department, Natural History Museum of Los Angeles County, Los Angeles, CA, USA
Joe Marty
Affiliation:
Mineral Sciences Department, Natural History Museum of Los Angeles County, Los Angeles, CA, USA
Ronald B. Gibbs
Affiliation:
Department of Geosciences, University of Arizona, Tucson, AZ, USA
Robert T. Downs
Affiliation:
Department of Geosciences, University of Arizona, Tucson, AZ, USA
*
Corresponding author: Hexiong Yang; Email: hyang@arizona.edu
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Abstract

A new oxalate mineral species, edwindavisite, ideally Cu(C2O4)(NH3), was discovered in specimens collected from the Rowley mine, Maricopa County, Arizona, USA. It occurs as fans or sprays of bladed or prismatic crystals (up to 0.50 × 0.08 × 0.06 mm), associated intimately with ammineite, a sampleite-like mineral, baryte, ebnerite, wulfenite and quartz. Edwindavisite is green, transparent with a pale green streak and has a vitreous lustre. It is brittle and has a Mohs hardness of ∼2; cleavage is perfect on {100}. No parting or twinning was observed. The measured and calculated densities are 2.55(2) and 2.53 g/cm3, respectively. Optically, edwindavisite is biaxial (+), with α = 1.550(2), β = 1.559(2), γ = 1.755(5), 2Vmeas. = 26(2)° and 2Vcal. = 26.4°. Electron microprobe analyses yielded the empirical formula (based on Cu = 1 apfu) Cu1.00(C2O4)(NH3)0.99.

Edwindavisite is the natural counterpart of synthetic catena-μ-oxalato-ammine-copper(II), Cu(C2O4)(NH3). It is orthorhombic with space group Pbca and unit-cell parameters a = 11.1998(10), b = 9.4307(9), c = 8.3977(7) Å, V = 886.98(14) Å3 and Z = 8. In the edwindavisite structure, each Cu2+ cation is coordinated by (5O + N), forming a rather distorted and elongated octahedron. The Cu-octahedra share corners with one another to form chains extending along [001], which are joined together by oxalate (C2O4)2– groups, giving rise to layers parallel to (100). These layers are linked together by N–H···O hydrogen bonds. Among 37 oxalate minerals documented to date, edwindavisite is the first one that contains ammonia (NH3).

Keywords

edwindavisiteoxalateammoniacrystal structureX-ray diffractionRaman spectroscopybat guanoRowley mineArizona

Information

Type
Article
Information
Mineralogical Magazine , Volume 89 , Issue 4 , August 2025 , pp. 535 - 543
Creative Commons
Creative Common License - CCCreative Common License - BY
This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/licenses/by/4.0), which permits unrestricted re-use, distribution and reproduction, provided the original article is properly cited.
Copyright
© The Author(s), 2025. Published by Cambridge University Press on behalf of The Mineralogical Society of the United Kingdom and Ireland.

Introduction

Oxalate minerals are the largest subclass of organic minerals. In the current list of minerals approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (IMA-CNMNC, Pasero, Reference Pasero2025), those derived from organic acids include three acetates, one citrate, two formates, seven glycolates, one mellitate, one methanesulfonate and 37 oxalates. While some oxalate minerals may form abiotically, most are found to occur in connection with biological systems. They are known to form when sources of oxalic acid interact with metal cations leached from primary minerals (e.g. Baran and Monje, Reference Baran and Monje2008; Baran, Reference Baran2014; Frank-Kamenetskaya et al., Reference Frank-Kamenetskaya, Zelenskaya, Izatulina, Vereshchagin, Vlasov, Himelbrant and Pankin2021). In biologically induced mineralisation, acid-producing microorganisms, such as fungi, lichens and bacteria, as well as guano, are common sources of oxalic acid (e.g. Baran, Reference Baran2014; Gadd et al., Reference Gadd, Bahri-Esfahani, Li, Rhee, Wei, Fomina and Liang2014). Moreover, oxalates represent the only ionic organic minerals known to be stable over geological timescales on Earth (Hoffman and Bernasconi, Reference Hofmann and Bernasconi1998; Hazen et al., Reference Hazen, Downs, Jones and Kah2013). Thus, their presence may be an indicator of plant life either current or in pre-existing life forms.

Oxalate materials have been the subject of various investigations owing to their diverse applications, such as hydrogen storage, carbon sequestration, catalysis, gas separation and photovoltaics (e.g. de Faria et al., Reference de Faria, Yoshida, Pinheiro, Guedes, Krambrock, Diniz and Machado2007; Androš et al., Reference Androš, Jurić, Planinić, Žilić, Rakvin and Molčanov2010; Furukawa et al., Reference Furukawa, Cordova, O’Keeffe and Yaghi2013; Garcia-Teran et al., Reference Garcia-Teran, Beobide, Castillo, Cepeda, Luque, Perez-Yanez and Roman2019). In particular, the study of the crystallisation of copper oxalate is very interesting and promising, because copper is a toxic element and the formation of insoluble copper oxalate can be used in bioremediation technologies for copper-contaminated environments with the help of oxalate-producing microorganisms (e.g. Fomina et al., Reference Fomina, Hillier, Charnock, Melville, Alexander and Gadd2005; Ren et al., Reference Ren, Li, Geng and Li2009; Tsekova et al., Reference Tsekova, Todorova and Ganeva2010; Gadd et al., Reference Gadd, Bahri-Esfahani, Li, Rhee, Wei, Fomina and Liang2014; Glukhova et al., Reference Glukhova, Frank, Danilova, Avakyan, Banks, Tuovinen and Karnachuk2018). For example, Tsekova et al. (Reference Tsekova, Todorova and Ganeva2010) described the recovery of copper and other metals from industrial wastewater using Aspergillus niger, which is one of the most commonly used oxalate-producing micromycetes (Gadd et al., Reference Gadd, Bahri-Esfahani, Li, Rhee, Wei, Fomina and Liang2014; Zelenskaya et al., Reference Zelenskaya, Izatulina, Frank-Kamenetskaya and Vlasov2021; Frank-Kamenetskaya et al., Reference Frank-Kamenetskaya, Zelenskaya, Izatulina, Gurzhiy, Rusakov and Vlasov2022). Moreover, there have been numerous publications on the application of Cu-oxalates in industry for their interesting physical and chemical properties, including use as antiferromagnets (e.g. Donkova and Mehandjiev, Reference Donkova and Mehandjiev2005; Behnoudnia and Dehghani, Reference Behnoudnia and Dehghani2013), and for their acting as a precursors to the formation of a number of widely used nanoparticles, such as Cu, CuO, Cu2O and Cu(OH)2 (e.g. Aimable et al., Reference Aimable, Puentes and Bowen2011; Singh et al., Reference Singh, Kapoor, Dubey and Srivastava2012; Gadd et al., Reference Gadd, Bahri-Esfahani, Li, Rhee, Wei, Fomina and Liang2014; Wu and Huang, Reference Wu and Huang2016).

Figure 1. A specimen (R230005) on which the new mineral edwindavisite (indicated by red arrows), was found.

Figure 2. A microscopic view of Fig. 1 showing fans of green bladed edwindavisite crystals, associated with a blue sampleite-like phase and ammineite.

Figure 3. Back-scattered electron images (a and b), showing fans of prismatic or bladed edwindavisite crystals.

This study describes a new oxalate mineral, edwindavisite, ideally Cu(C2O4)(NH3), discovered from the Rowley mine, Maricopa County, Arizona, USA. The new mineral name honours Mr. F. Edwin (Ed) Davis, Jr., an Arizona-based mineral collector and the current contractor operator of the Rowley mine, who has gladly accepted the proposed mineral name. Ed Davis graduated from Miami University in Oxford, Ohio, USA, with degrees in chemical engineering, mathematics and chemistry. He is credited for the discovery of the Purple Passion deposit near Wickenburg, Arizona, USA, which is world-renowned among fluorescent mineral collectors. Ed Davis has helped in the collection of multiple new minerals from the Rowley mine, such as ebnerite and epiebnerite (Kampf et al., Reference Kampf, Gu, Yang, Ma and Marty2024), as well as edwindavisite described here. In particular, he provided access to the mine, helped in exploration, and helped in removing specimens from difficult to negotiate underground workings. The new mineral and its name (symbol Ewd) have been approved by the IMA (IMA 2023-056, Yang et al., Reference Yang, Gu, Kampf, Marty, Gibbs and Downs2023). Parts of the cotype samples have been deposited at the University of Arizona Alfie Norville Gem and Mineral Museum (Catalogue # 22732) and the RRUFF Project (deposition # R230003). In addition, two cotype specimens are deposited in the collections of the Natural History Museum of Los Angeles County, Los Angeles, California, USA (catalogue numbers 76287 and 76288).

Sample description and experimental methods

Occurrence

Edwindavisite was discovered on specimens collected on the 125-foot level of the Rowley mine, ∼20 km NW of Theba, Maricopa County, Arizona, USA (33°257’N, 113°149.59’W). This mine is a former Cu-Pb-Au-Ag-Mo-V-baryte-fluorspar mine that exploited veins presumed to be related to the intrusion of an andesite porphyry dyke into Tertiary volcanic rocks. The mine has not been operated for ore since 1923, but it has been a rich source of fine wulfenite crystals for mineral collectors in the past 70 years. A detailed description of the history, geology and mineralogy of the Rowley mine has been presented by Wilson (Reference Wilson2020). Edwindavisite was found on a quartz matrix, in intimate association with ammineite, a sampleite-like mineral, baryte, ebnerite and wulfenite (Fig. 1). The area where the edwindavisite specimens were collected has an unusual bat guano-related, secondary mineral assemblage, from which a number of new mineral species have been discovered, including rowleyite (Kampf et al., Reference Kampf, Cooper, Nash, Cerling, Marty, Hummer, Celestian, Rose and Trebisky2017), phoxite (Kampf et al., Reference Kampf, Celestian, Nash and Marty2019b), davidbrownite-(NH4) (Kampf et al., Reference Kampf, Cooper, Rossman, Nash, Hawthorne and Marty2019a), natrosulfatourea (Kampf et al., Reference Kampf, Celestian, Nash and Marty2021a), allantoin (Kampf et al., Reference Kampf, Celestian, Nash and Marty2021a), thebaite-(NH4) (Kampf et al., Reference Kampf, Cooper, Celestian, Nash and Marty2021b), relianceite-(K) (Kampf et al., Reference Kampf, Cooper, Celestian, Ma and Marty2022a), dendoraite-(NH4) (Kampf et al., Reference Kampf, Cooper, Celestian, Ma and Marty2022a), ebnerite, epiebnerite (Kampf et al. Reference Kampf, Gu, Yang, Ma and Marty2024), ferriphoxite and carboferriphoxite (Kampf et al., Reference Kampf, Ma, Hawthorne and Marty2025a).

Figure 4. Raman spectra of edwindavisite, whewellite and ammineite.

Appearance, physical and chemical properties

Edwindavisite occurs as radial fans or sprays of bladed or prismatic crystals, elongated on [001]. Individual crystals are up to 0.50 × 0.08 × 0.06 mm (Figs 2 and 3), with the common forms being {100}, {010} and {001}. It is green, transparent with a pale green streak and vitreous lustre. Edwindavisite is brittle and has a Mohs hardness of ∼2 (based on scratch tests); cleavage is perfect on {100}. No parting was observed. The density, measured by flotation in heavy liquids, is 2.55(2) g/cm3 and the calculated density is 2.53 g/cm3 on the basis of the empirical chemical formula and the unit-cell volume determined from single-crystal X-ray diffraction data. Optically, edwindavisite is biaxial (+), with α = 1.550(2), β = 1.559(2), γ = 1.755(5) (white light), 2Vmeas. = 26(2)° and 2Vcal. = 26.4°. The dispersion is distinct with r > v. The optical orientation is X = a, Y = c, Z = b, and the pleochroism is X = light green, Y = pale green and Z = deep green, with Y < X ≪ Z. The compatibility index was not calculated, because of the lack of a k-value for the NH3 group. Based on the measured optical data and density, along with an ideal chemical formula, we derived an estimated k-value of 0.495 for the NH3 molecule. Given this k-value for NH3, we obtained a compatibility index of –0.005 (superior) for edwindavisite and –0.018 (superior) for shilovite, Cu(NH3)4(NO3)2, with the data reported by Chukanov et al. (Reference Chukanov, Britvin, Möhn, Pekov, Zubkova, Nestola, Kasatkin and Dini2015).

Table 5. Fractional atom coordinates and isotropic or equivalent isotropic displacement parameters (Å2) for edwindavisite

Table 6. Anisotropic displacement parameters (Å2) for edwindavisite

Table 7. Selected bond distances (Å) for edwindavisite

Table 8. Hydrogen-bond geometry (Å, °) in edwindavisite

Notes: Symmetry codes: (ii) x, −y+½, z+½; (v) x+½, y, −z+½; (vi) x+½, −y+½, −z; (vii) −x+½, y+½, z. D = donor; A = acceptor.

Table 9. Bond-valence sums (vu) for edwindavisite

Note: The significant deviation of bond-valence sums from the ideal values for N3+ and H+ ions is due to the fact that the bond-valence parameters (R 0 = 0.935 Å and B = 0.572 Å) given by Gagné (Reference Gagné2021) were derived from the neutron diffraction data based on the average N–H distance of 0.999 Å (with a range of 0.915–1.025 Å). This N–H distance is remarkably longer than any reported N–H distances determined from the X-ray structure analyses for the NH3 group (0.7–0.9 Å). If we constrain our N–H distance to be 0.95 Å, then we have the bond valence sums of 3.48 vu for N and 0.97 vu for H.

Figure 5. The configuration of the Cu atom coordinated octahedrally by (5O + N) in edwindavisite. The structures were drawn using VESTA (Momma and Izumi, Reference Momma and Izumi2011).

Figure 6. A corner-sharing Cu-octahedral chain in (a) edwindavisite and (b) triazolite.

Figure 7. A layer of corner-sharing Cu-octahedral chains linked together by oxalate groups in edwindavisite. The figure legends are the same as in Fig. 5.

Figure 8. Crystal structure of edwindavisite, showing the Cu(C2O4)(NH3) layers stacked along [100], which are interconnected by N–H···O hydrogen bonds provided by NH3 ammonia molecules. For clarity and simplicity, N–H···O hydrogen bonds between Cu(C2O4)(NH3) layers are not drawn. The figure legends are the same as in Fig. 5.

The chemical composition of edwindavisite was determined using a Shimadzu EPMA-1720 electron microprobe (WDS mode, 15 kV, 10 nA and 5 μm beam diameter). The analytical data (average of 7 analysis points) are given in Table 1, along with the standards used for the probe analyses. The resultant empirical chemical formula, calculated on the basis of 1 Cu apfu, is Cu1.00(C2O4)(NH3)0.99. The hydrogen content was calculated by stoichiometry. The ideal formula, Cu(C2O4)(NH3), requires (wt.%) CuO 47.18, C2O3 42.72, NH3 10.10 (total = 100%). At room temperature, edwindavisite is insoluble in H2O, but easily soluble in dilute HCl.

Table 1. Analytical chemical data (in wt.%) for edwindavisite

Raman spectra

The Raman spectrum of edwindavisite (Fig. 4) was collected from a randomly orientated crystal on a Thermo Almega microRaman system, using a solid-state laser with a frequency of 532 nm at 50 mW power (1/3 of the full power to avoid the burning by the laser) and a thermoelectric cooled CCD detector. The laser is partially polarised with 4 cm–1 resolution and a spot size of 1 µm.

The tentative assignments of major Raman bands for edwindavisite were made based on spectroscopic studies on materials containing oxalate (C2O4)2– and/or ammine groups, such as synthetic edwindavisite Cu(C2O4)(NH3) (Cavalca et al., Reference Cavalca, Villa, Manfredotti, Mangia and Tomlinson1972), ammineite CuCl2(NH3)2 (Bojar et al., Reference Bojar, Walter, Baumgartner and Färber2010), humboldtine Fe2+(C2O4)·2H2O (Frost and Weier, Reference Frost and Weier2003; Echigo and Kimata, Reference Echigo and Kimata2008), whewellite Ca(C2O4)·H2O (Shippey, Reference Shippey1980; Frost and Weier, Reference Frost and Weier2003), and shilovite Cu(NH3)4(NO3)2 (Chukanov et al., Reference Chukanov, Britvin, Möhn, Pekov, Zubkova, Nestola, Kasatkin and Dini2015). Specifically, the Raman spectrum of edwindavisite can be divided into five regions (Table 2). Region 1 ranges from 3160 to 3450 cm–1, with a relatively strong peak centred at 3287 cm–1. The bands in this region are due to the N–H stretching modes in NH3 groups. Region 2 includes the bands between 1120 and 1735 cm–1, which are ascribable to the C=O and C–O stretching vibrations within the C2O4 groups, as well as the H–N–H bending modes within the NH3 groups. In particular, the two sharp peaks, one at 1508 cm–1 and the other at 1454 cm–1, correspond to the symmetric stretching vibrations of C=O and C–O bonds within C2O4. It is interesting to note that whewellite only shows one strong peak at 1493 cm–1 in this region, whereas both oxammite, (NH4)2(C2O4)·H2O and moolooite, Cu(C2O4)·nH2O, exhibit two relatively strong peaks (Frost and Weier, Reference Frost and Weier2003). Region 3 spans the region from 840 to 950 cm–1. The sharp peak at 908 cm–1 in this region is assigned to the C–C stretching vibrations and the weak bands are attributed to the O–C–O antisymmetric bending modes within the C2O4 groups. In comparison, the band corresponding to the C–C stretching vibrations is observed at 909 cm–1 for weddellite and 921 cm–1 for moolooite (Frost and Weier, Reference Frost and Weier2003). Region 4 ranges from 440 to 620 cm–1. The strong peak at 518 cm–1 in the region corresponds to the C–C–O bending mode and the rest of the bands can be attributed to the Cu–O stretching modes involving the shortest Cu–O bonds. Region 5 includes the bands below 350 cm–1, which are associated mainly with the rotational and translational modes of C2O4 and NH3 groups, as well as the Cu2+–(O,N) interactions and lattice vibrational modes. For comparison, the Raman spectra of ammineite and whewellite from the RRUFF Project (Lafuente et al., Reference Lafuente, Downs, Yang, Stone, Armbruster and Danisi2015) are also plotted in Fig. 4.

Table 2. Tentative assignments of major Raman bands for edwindavisite

X-ray crystallography

Powder X-ray diffraction data for edwindavisite were collected on a Rigaku Xtalab Synerg D/S 4-circle diffractometer equipped with CuK radiation and operated at 50 kV and 1 mA. Powder X-ray diffraction data (Table 3) were collected in the Gandolfi powder mode and the unit-cell parameters refined using the program by Holland and Redfern (Reference Holland and Redfern1997) are: a = 11.2011(4), b = 9.4260(3), c = 8.4042(3) Å and V = 887.33(3) Å3.

Table 3. Powder X-ray diffraction data (d in Å, I in %) for edwindavisite

Single-crystal X-ray diffraction data of edwindavisite were collected on a Bruker APEX2 4-circle diffractometer equipped with MoK radiation from a 0.06 × 0.05 × 0.05 mm fragment. All reflections were indexed on the basis of an orthorhombic unit cell (Table 4). The systematic absences of reflections suggest the unique space group Pbca. The structure was solved with SHELXT (Sheldrick, Reference Sheldrick2015a) and refined using SHELXL2019 (Sheldrick, Reference Sheldrick2015b). All H atoms were located through the difference-Fourier syntheses. The positions of all atoms were refined with anisotropic displacement parameters, except for H atoms, which were refined with a fixed isotropic displacement parameter (U iso = 0.05 Å2) and soft restraints of 0.85(3) Å on the N–H distances. The final refinement statistics are listed in Table 3. Atomic coordinates and displacement parameters are given in Tables 5 and 6, respectively. Selected bond distances are presented in Table 7 and hydrogen bonding geometries in Table 8. The bond-valence sums (BVS) were calculated using the parameters given by Brown (Reference Brown2009) for Cu–O and Cu–N bonds, Harris and Hardcastle (Reference Harris and Hardcastle2015) for C–C and C–O bonds, Gagné (Reference Gagné2021) for N–H bonds, and by Ferraris and Ivaldi (Reference Ferraris and Ivaldi1988) for O···H bonds (Table 9). The crystallographic information file has been deposited with the Principal Editor of Mineralogical Magazine and is available as Supplementary material (see below).

Table 4. Crystallographic data for natural and synthetic edwindavisite

Crystal structure description and discussion

Edwindavisite is the natural analogue of synthetic catena-μ-oxalato-ammine-copper(II), Cu(C2O4)(NH3) (Cavalca et al., Reference Cavalca, Villa, Manfredotti, Mangia and Tomlinson1972) (Table 4). In its structure, each Cu2+ cation is coordinated by (5O + N), forming a rather distorted and elongated octahedron (Fig. 5) due to the Jahn-Teller effect. The five O atoms coordinated to a Cu atom are from three different (C2O4)2– groups, two being bidentately bonded and one monodentately bonded, with the Cu–O bond lengths ranging from 1.983 to 2.399 Å. The Cu–N distance (1.966 Å) is shorter than any of the Cu–O distances, but agrees well with the values reported for Cu that is bonded to NH3 (Bojar et al., Reference Bojar, Walter, Baumgartner and Färber2010 and references therein).

The Cu-octahedra in the edwindavisite structure share corners with one another to form chains extending along [001] (Fig. 6), which are joined together by oxalate (C2O4)2– groups, giving rise to layers parallel to (100) (Fig. 7). Such layers are interconnected by N–H···O hydrogen bonds (Table 8, Fig. 8). Similar chains of corner-sharing Cu-octahedra have also been observed in triazolite, NaCu2(N3C2H2)2(NH3)2Cl3·4H2O (Chukanov et al., Reference Chukanov, Zubkova, Möhn, Pekov, Belakovskiy, Van and Pushcharovsky2018) (Fig. 6), and pabellóndepicaite, Cu2+2(N3C2H2)2(NH3)2(NO3)Cl·2H2O (Kampf et al., Reference Kampf, Möhn, Ma and Désor2025b), both being Cu-bearing organic minerals containing 1,2,4-triazolate anions, as well as NH3 molecules.

Oxalic acid is ubiquitous in natural environments. It can be produced by some plants, fungi and lichens (e.g. Dutton and Evans, Reference Dutton and Evans1996; Prieto et al., Reference Prieto, Silva, Rivas, Wierzchos and Ascaso1997; Chen et al., Reference Chen, Blume and Beyer2000; Grąz, Reference Grąz2024). Lichens and fungi living on mineral surfaces have been found to facilitate the dissolution of heavy metals (e.g. Chisholm et al., Reference Chisholm, Jones and Purvis1987; Fomina et al., Reference Fomina, Hillier, Charnock, Melville, Alexander and Gadd2005; Studenroth et al., Reference Studenroth, Huber, Kotte and H.F2013; Schuler et al., Reference Schuler, Demetriou, Shiju and Gruter2021; Amenaghawon et al., Reference Amenaghawon, Ayere, Amune, Otuya, Abuga, Anyalewechi and Darmokoesoemo2024). Yet, only 37 oxalate minerals have been documented to date. Among them, six contain Cu [antipinite, KNa3Cu2(C2O4)4, edwindavisite, fiemmeite, Cu2(C2O4)(OH)2·2H2O, middlebackite, Cu2C2O4(OH)2, moolooite, Cu(C2O4)·nH2O, and wheatleyite, Na2Cu(C2O4)2·2H2O], and seven contain ammonium (NH4)+ [davidbrownite-(NH4), (NH4)5(V4+O)2(C2O4)[PO2.75(OH)1.25]4·3H2O, dendoraite-(NH4), (NH4)2NaAl(C2O4)(PO3OH)2(H2O)2, oxammite, (NH4)2(C2O4)·H2O, phoxite (NH4)2Mg2(C2O4)(PO3OH)2(H2O)4, thebaite-(NH4), (NH4)3Al(C2O4)(PO3OH)2(H2O), ferriphoxite, [(NH4)2K(H2O)][Fe3+(HPO4)2(C2O4)], and carboferriphoxite, [(NH4)K(H2CO3)][Fe3+(HPO4)(H2PO4)(C2O4)]]. Edwindavisite represents the first oxalate mineral that contains neutral ammonia (NH3).

Nitrogen is usually present in minerals as (NO3)– or (NH4)+ ionic groups. In the current IMA-approved mineral list (Pasero, Reference Pasero2025), only seven minerals contain the neutral ammonia molecule (NH3) as a species-defining component: ammineite, CuCl2·2NH3, chanabayaite, Cu2Cl(N3C2H2)2(NH3,Cl,H2O,◻)4, joanneumite, Cu(C3N3O3H2)2(NH3)2, pabellóndepicaite, Cu2+2(N3C2H2)2(NH3)2(NO3)Cl·2H2O, shilovite, Cu(NH3)4(NO3)2, triazolite, NaCu2(N3C2H2)2(NH3)2Cl3·4H2O, and edwindavisite. Interestingly, all these minerals have only been described in the past 20 years. Among them, all but edwindavisite were discovered at Pabellón de Pica, Iquique Province, Chile. Moreover, all of them have Cu2+ as the essential component and bonded to NH3. Nonetheless, it is unclear how the presence of Cu2+ is related to the formation of NH3-bearing minerals.

Supplementary material

The supplementary material for this article can be found at https://doi.org/10.1180/mgm.2025.16

Acknowledgements

We are very grateful to Prof Peter Leverett and two anonymous reviewers for their constructive comments.

Competing interests

The authors declare none.

Footnotes

Associate Editor: Irina O Galuskina

References

Aimable, A., Puentes, A.T. and Bowen, P. (2011) Synthesis of porous and nanostructured particles of CuO via a copper oxalate route. Powder Technology, 208, 467–471.10.1016/j.powtec.2010.08.044CrossRefGoogle Scholar
Amenaghawon, A.N., Ayere, J.E., Amune, U.O., Otuya, I.C., Abuga, E.C. Anyalewechi, C.L. and Darmokoesoemo, H. (2024) A comprehensive review of recent advances in the applications and biosynthesis of oxalic acid from bio-derived substrates. Environmental Research, 251, 118703.10.1016/j.envres.2024.118703CrossRefGoogle ScholarPubMed
Androš, L., Jurić, M., Planinić, P., Žilić, D., Rakvin, B. and Molčanov, K. (2010) New mononuclear oxalate complexes of copper (II) with 2D and 3D architectures: Synthesis, crystal structures and spectroscopic characterization. Polyhedron, 29, 1291–1298.10.1016/j.poly.2010.01.005CrossRefGoogle Scholar
Baran, E.J. (2014) Natural oxalates and their analogous synthetic complexes. Journal of Coordination Chemistry, 67, 3734–3768.CrossRefGoogle Scholar
Baran, E.J. and Monje, P.V. (2008) Oxalate biominerals. Biomineralization: From Nature to Application, 4, 219–254.10.1002/9780470986325.ch7CrossRefGoogle Scholar
Behnoudnia, F. and Dehghani, H. (2013) Copper (II) oxalate nanospheres and its usage in preparation of Cu(OH)2, Cu2O and CuO nanostructures: Synthesis and growth mechanism. Polyhedron, 56, 102–108.10.1016/j.poly.2013.03.051CrossRefGoogle Scholar
Bojar, H.P., Walter, F., Baumgartner, J. and Färber, G. (2010) Ammineite, CuCl2(NH3)2, a new species containing an ammine complex: Mineral data and crystal structure. The Canadian Mineralogist, 48, 1359–1371.10.3749/canmin.48.5.1359CrossRefGoogle Scholar
Brown, I.D. (2009) Recent developments in the methods and applications of the bond valence model. Chemical Reviews, 109, 6858–6919.10.1021/cr900053kCrossRefGoogle Scholar
Cavalca, L., Villa, A.C., Manfredotti, A.G., Mangia, A. and Tomlinson, A.A.G. (1972) Crystal, molecular and electronic structure of catena-µ-oxalato-ammine-copper (II). Journal of the Chemical Society Dalton Transactions, 3, 391–395.10.1039/DT9720000391CrossRefGoogle Scholar
Chen, J., Blume, H.P. and Beyer, L. (2000) Weathering of rocks induced by lichen colonization—a review. Catena, 39, 121–146.10.1016/S0341-8162(99)00085-5CrossRefGoogle Scholar
Chisholm, J.E., Jones, G.C. and Purvis, O.W. (1987) Hydrated copper oxalate, moolooite, in lichens. Mineralogical Magazine, 51, 715–718.10.1180/minmag.1987.051.363.12CrossRefGoogle Scholar
Chukanov, N.V., Britvin, S.N., Möhn, G., Pekov, I.V., Zubkova, N.V., Nestola, F., Kasatkin, A.V. and Dini, M. (2015) Shilovite, natural copper(II) tetrammine nitrate, a new mineral species. Mineralogical Magazine, 79, 613–623.10.1180/minmag.2015.079.3.07CrossRefGoogle Scholar
Chukanov, N.V., Zubkova, N.V., Möhn, G., Pekov, I.V., Belakovskiy, D.I., Van, K.V. and Pushcharovsky, D.Y. (2018) Triazolite, NaCu2(N3C2H2)2(NH3)2Cl3·4H2O, a new mineral species containing 1, 2, 4-triazolate anion, from a guano deposit at Pabellón de Pica, Iquique Province, Chile. Mineralogical Magazine, 82, 1007–1014.10.1180/minmag.2017.081.088CrossRefGoogle Scholar
de Faria, D.M., Yoshida, M.I., Pinheiro, C.B., Guedes, K.J., Krambrock, K., Diniz, R. and Machado, F.C. (2007) Preparation, crystal structures and spectroscopic characterization of oxalate copper (II) complexes containing the nitrogen ligands 4, 4-dimethyl-2, 2-bipyridine and di (2-pyridyl) sulfide. Polyhedron, 26, 4525–4532.10.1016/j.poly.2007.06.027CrossRefGoogle Scholar
Donkova, B. and Mehandjiev, D. (2005) Review Thermal—Magnetic investigation of the decomposition of copper oxalate—A precursor for catalysts. Journal of Materials Science, 40, 3881–3886.10.1007/s10853-005-0487-0CrossRefGoogle Scholar
Dutton, M.V. and Evans, C.S. (1996) Oxalate production by fungi: its role in pathogenicity and ecology in the soil environment. Canadian Journal of Microbiology, 42, 881–895.10.1139/m96-114CrossRefGoogle Scholar
Echigo, T. and Kimata, M. (2008) Single-crystal X-ray diffraction and spectroscopic studies on humboldtine and lindbergite: weak Jahn-Teller effect of Fe2+ ion. Physics and Chemistry of Minerals, 35, 467–475.10.1007/s00269-008-0241-7CrossRefGoogle Scholar
Ferraris, G. and Ivaldi, G. (1988) Bond valence vs bond length in O⋯ O hydrogen bonds. Acta Crystallographica, B44, 341–344.10.1107/S0108768188001648CrossRefGoogle Scholar
Fomina, M., Hillier, S., Charnock, J.M., Melville, K., Alexander, I.J. and Gadd, G.M. (2005) Role of oxalic acid overexcretion in transformations of toxic metal minerals by Beauveria caledonica. Applied and Environmental Microbiology, 71, 371–381.10.1128/AEM.71.1.371-381.2005CrossRefGoogle ScholarPubMed
Frank-Kamenetskaya, O.V., Zelenskaya, M.S., Izatulina, A.R., Vereshchagin, O.S., Vlasov, D.Y., Himelbrant, D.E. and Pankin, D.V. (2021) Copper oxalate formation by lichens and fungi. Scientific Reports, 11, 24239.10.1038/s41598-021-03600-5CrossRefGoogle ScholarPubMed
Frank-Kamenetskaya, O., Zelenskaya, M., Izatulina, A., Gurzhiy, V., Rusakov, A. and Vlasov, D. (2022) Oxalate formation by Aspergillus niger on minerals of manganese ores. American Mineralogist, 107, 100–109.10.2138/am-2021-7651CrossRefGoogle Scholar
Frost, R.L. and Weier, M.L. (2003) Raman spectroscopy of natural oxalates at 298 and 77 K. Journal of Raman Spectroscopy, 34, 776–785.10.1002/jrs.1052CrossRefGoogle Scholar
Furukawa, H., Cordova, K.E., O’Keeffe, M. and Yaghi, O.M. (2013) The chemistry and applications of metal-organic frameworks. Science, 341, 1230444.10.1126/science.1230444CrossRefGoogle Scholar
Gadd, G.M., Bahri-Esfahani, J., Li, Q., Rhee, Y.J., Wei, Z., Fomina, M. and Liang, X. (2014) Oxalate production by fungi: significance in geomycology, biodeterioration and bioremediation. Fungal Biology Reviews, 28, 36–55.10.1016/j.fbr.2014.05.001CrossRefGoogle Scholar
Gagné, O.C. (2021) On the crystal chemistry of inorganic nitrides: crystal-chemical parameters, bonding behavior, and opportunities in the exploration of their compositional space. Chemical Science, 12, 4599–4622.10.1039/D0SC06028CCrossRefGoogle ScholarPubMed
Garcia-Teran, J.P., Beobide, G., Castillo, O., Cepeda, J., Luque, A., Perez-Yanez, S. and Roman, P. (2019) Supramolecular architectures of metal-oxalato coordination polymers bearing N-tethered adenine nucleobases. Polyhedron, 171, 53–64.10.1016/j.poly.2019.07.001CrossRefGoogle Scholar
Glukhova, L.B., Frank, Y.A., Danilova, E.V., Avakyan, M.R., Banks, D., Tuovinen, O.H. and Karnachuk, O.V. (2018) Isolation, characterization, and metal response of novel, acid-tolerant Penicillium spp. from extremely metal-rich waters at a mining site in Transbaikal (Siberia, Russia). Microbial Ecology, 76, 911–924.10.1007/s00248-018-1186-0CrossRefGoogle Scholar
Grąz, M. (2024) Role of oxalic acid in fungal and bacterial metabolism and its biotechnological potential. World Journal of Microbiology and Biotechnology, 40, 178 (1–11).10.1007/s11274-024-03973-5CrossRefGoogle ScholarPubMed
Harris, C. and Hardcastle, F.D. (2015) Bond length-bond valence relationships for carbon-carbon and carbon-oxygen bonds. Journal of the Arkansas Academy of Science, 69, 45–53.10.54119/jaas.2015.6905CrossRefGoogle Scholar
Hazen, R.M., Downs, R.T., Jones, A.P. and Kah, L. (2013) Carbon mineralogy and crystal chemistry. Reviews in Mineralogy and Geochemistry, 75, 7–46.10.2138/rmg.2013.75.2CrossRefGoogle Scholar
Hofmann, B.A. and Bernasconi, S.M. (1998) Review of occurrences and carbon isotope geochemistry of oxalate minerals: implications for the origin and fate of oxalate in diagenetic and hydrothermal fluids. Chemical Geology, 149, 127–146.10.1016/S0009-2541(98)00043-6CrossRefGoogle Scholar
Holland, T.J.B. and Redfern, S.A.T. (1997) Unit cell refinement from powder diffraction data: the use of regression diagnostics. Mineralogical Magazine, 61, 65–77.10.1180/minmag.1997.061.404.07CrossRefGoogle Scholar
Kampf, A.R., Cooper, M.A., Nash, B.P., Cerling, T., Marty, J., Hummer, D.R., Celestian, A.J., Rose, T.P. and Trebisky, T.J. (2017) Rowleyite, [Na(NH4,K)9Cl4][V5+,4+2(P,As)O8]6 ·n,[H2O,Na,NH4,K,Cl], a new mineral with a mesoporous framework structure. American Mineralogist, 102, 1037–1044.Google Scholar
Kampf, A.R., Cooper, M.A., Rossman, G.R., Nash, B.P., Hawthorne, F.C. and Marty, J. (2019a) Davidbrownite-(NH4), (NH4,K)5(V4+O)2(C2O4)[PO2.75(OH)1.25]4·3H2O, a new phosphate-oxalate mineral from the Rowley mine, Arizona, USA. Mineralogical Magazine, 84, 869–877.10.1180/mgm.2019.56CrossRefGoogle Scholar
Kampf, A.R., Celestian, A.J., Nash, B.P. and Marty, J. (2019b) Phoxite, (NH4)2Mg2(C2O4)(PO3OH)2(H2O)4, the first phosphate-oxalate mineral. American Mineralogist, 103, 973–979.10.2138/am-2019-6991CrossRefGoogle Scholar
Kampf, A.R., Celestian, A.J., Nash, B.P. and Marty, J. (2021a) Allantoin and natrosulfatourea, two new bat-guano minerals from the Rowley mine, Maricopa County, Arizona, U.S.A. The Canadian Mineralogist, 59, 603–616.10.3749/canmin.2000088CrossRefGoogle Scholar
Kampf, A.R., Cooper, M.A., Celestian, A.J., Nash, B.P. and Marty, J. (2021b) Thebaite-(NH4), (NH4,K)3Al(C2O4)(PO3OH)2(H2O), a new phosphate-oxalate mineral from the Rowley mine, Arizona, USA. Mineralogical Magazine, 85, 379–386.10.1180/mgm.2021.26CrossRefGoogle Scholar
Kampf, A.R., Cooper, M.A., Celestian, A.J., Ma, C. and Marty, J. (2022a) Dendoraite-(NH4), a new phosphate-oxalate mineral related to thebaite-(NH4) from the Rowley mine, Arizona, USA. Mineralogical Magazine, 86, 531–538.10.1180/mgm.2021.98CrossRefGoogle Scholar
Kampf, A.R., Cooper, M.A., Celestian, A.J., Ma, C. and Marty, J. (2022b) Relianceite-(K), a new phosphate-oxalate mineral related to davidbrownite-(NH4) from the Rowley mine, Arizona USA. Mineralogical Magazine, 86, 539–547.10.1180/mgm.2021.99CrossRefGoogle Scholar
Kampf, A.R., Gu, X., Yang, H., Ma, C. and Marty, J. (2024) Ebnerite and epiebnerite: NH4ZnPO4 dimorphs with zeolite-type frameworks from the Rowley mine Arizona USA. Mineralogical Magazine, 88, 312–318.10.1180/mgm.2024.15CrossRefGoogle Scholar
Kampf, A.R., Ma, C., Hawthorne, F.C. and Marty, J. (2025a) Ferriphoxite and carboferriphoxite: two new oxalato-phosphate minerals from the Rowley mine, Arizona, USA. Mineralogical Magazine, 89, 162–171. doi: 10.1180/mgm.2024.56.CrossRefGoogle Scholar
Kampf, A.R., Möhn, G., Ma, C. and Désor, J. (2025b) Pabellóndepicaite, Cu2+2(N3C2H2)2(NH3)2(NO3)Cl·2H2O, a new triazole mineral from the guano deposit at Pabellón de Pica, Iquique Province, Chile. Mineralogical Magazine, 89, 141–147. doi: 10.1180/mgm.2024.55.CrossRefGoogle Scholar
Lafuente, B., Downs, R.T., Yang, H., Stone, N., Armbruster, T. and Danisi, R.M. (2015) The power of databases: the RRUFF project. Highlights in Mineralogical Crystallography, 1, 25.Google Scholar
Momma, K. and Izumi, F. (2011) VESTA 3 for three-dimensional visualization of crystal, volumetric and morphology data. Journal of Applied Crystallography, 44, 1272–1276.10.1107/S0021889811038970CrossRefGoogle Scholar
Pasero, M. (2025) The New IMA List of Minerals. International Mineralogical Association. Commission on new minerals, nomenclature and classification (IMA-CNMNC). http://cnmnc.units.it/Google Scholar
Prieto, B., Silva, B., Rivas, T., Wierzchos, J. and Ascaso, C. (1997) Mineralogical transformation and neoformation in granite caused by the lichens Tephromela atra and Ochrolechia parella. International Biodeterioration and Biodegradation, 40, 191–199.10.1016/S0964-8305(97)00052-8CrossRefGoogle Scholar
Ren, W.X., Li, P.J., Geng, Y. and Li, X.J. (2009) Biological leaching of heavy metals from a contaminated soil by Aspergillus niger. Journal of Hazardous Materials, 167, 164–169.10.1016/j.jhazmat.2008.12.104CrossRefGoogle ScholarPubMed
Schuler, E., Demetriou, M., Shiju, N.R. and Gruter, G.J.M. (2021) Towards sustainable oxalic acid from CO2 and biomass. ChemSusChem, 14, 3636–3664.10.1002/cssc.202101272CrossRefGoogle ScholarPubMed
Sheldrick, G.M. (2015a) SHELXT – Integrated space-group and crystal structure determination. Acta Crystallographica, A71, 3–8.Google Scholar
Sheldrick, G.M. (2015b) Crystal structure refinement with SHELX. Acta Crystallographica, C71, 3–8.Google Scholar
Shippey, T.A. (1980) Vibrational studies of calcium oxalate monohydrate (whewellite) and an anhydrous phase of calcium oxalate. Journal of Molecular Structure, 63, 157–166.10.1016/0022-2860(80)80323-1CrossRefGoogle Scholar
Singh, G., Kapoor, I.P.S., Dubey, R. and Srivastava, P. (2012) Preparation, characterization and catalytic effects of copper oxalate nanocrystals. Journal of Alloys and Compounds, 513, 499–505.10.1016/j.jallcom.2011.10.100CrossRefGoogle Scholar
Studenroth, S., Huber, S.G., Kotte, K. and H.F, Schöler. (2013) Natural abiotic formation of oxalic acid in soils: results from aromatic model compounds and soil samples. Environmental Science & Technology, 47, 1323–1329.Google ScholarPubMed
Tsekova, K., Todorova, D. and Ganeva, S. (2010) Removal of heavy metals from industrial wastewater by free and immobilized cells of Aspergillus niger. International Biodeterioration & Biodegradation, 64, 447–451.10.1016/j.ibiod.2010.05.003CrossRefGoogle Scholar
Wilson, W.E. (2020) The Rowley mine, Painted Rock Mountains, Maricopa County, Arizona. Mineralogical Record, 51, 181–226.Google Scholar
Wu, J.Y. and Huang, K. (2016) Precipitation of flaky moolooite and its thermal decomposition. International Journal of Minerals Metallurgy and Materials, 23, 976–980.10.1007/s12613-016-1314-0CrossRefGoogle Scholar
Yang, H., Gu, X., Kampf, A.R., Marty, J., Gibbs, R.B. and Downs, R.T. (2023) Edwindavisite, IMA 2023-056. CNMNC Newsletter 75. Mineralogical Magazine, 87, https://doi.org/10.1180/mgm.2023.76Google Scholar
Zelenskaya, M.S., Izatulina, A.R., Frank-Kamenetskaya, O.V. and Vlasov, D.Y. (2021) Iron oxalate humboldtine crystallization by fungus Aspergillus niger. Crystals, 11, 1591.10.3390/cryst11121591CrossRefGoogle Scholar
Figure 0

Figure 1. A specimen (R230005) on which the new mineral edwindavisite (indicated by red arrows), was found.

Figure 1

Figure 2. A microscopic view of Fig. 1 showing fans of green bladed edwindavisite crystals, associated with a blue sampleite-like phase and ammineite.

Figure 2

Figure 3. Back-scattered electron images (a and b), showing fans of prismatic or bladed edwindavisite crystals.

Figure 3

Figure 4. Raman spectra of edwindavisite, whewellite and ammineite.

Figure 4

Table 5. Fractional atom coordinates and isotropic or equivalent isotropic displacement parameters (Å2) for edwindavisite

Figure 5

Table 6. Anisotropic displacement parameters (Å2) for edwindavisite

Figure 6

Table 7. Selected bond distances (Å) for edwindavisite

Figure 7

Table 8. Hydrogen-bond geometry (Å, °) in edwindavisite

Figure 8

Table 9. Bond-valence sums (vu) for edwindavisite

Figure 9

Figure 5. The configuration of the Cu atom coordinated octahedrally by (5O + N) in edwindavisite. The structures were drawn using VESTA (Momma and Izumi, 2011).

Figure 10

Figure 6. A corner-sharing Cu-octahedral chain in (a) edwindavisite and (b) triazolite.

Figure 11

Figure 7. A layer of corner-sharing Cu-octahedral chains linked together by oxalate groups in edwindavisite. The figure legends are the same as in Fig. 5.

Figure 12

Figure 8. Crystal structure of edwindavisite, showing the Cu(C2O4)(NH3) layers stacked along [100], which are interconnected by N–H···O hydrogen bonds provided by NH3 ammonia molecules. For clarity and simplicity, N–H···O hydrogen bonds between Cu(C2O4)(NH3) layers are not drawn. The figure legends are the same as in Fig. 5.

Figure 13

Table 1. Analytical chemical data (in wt.%) for edwindavisite

Figure 14

Table 2. Tentative assignments of major Raman bands for edwindavisite

Figure 15

Table 3. Powder X-ray diffraction data (d in Å, I in %) for edwindavisite

Figure 16

Table 4. Crystallographic data for natural and synthetic edwindavisite

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