Eur. J. Mineral., 33, 659–673, 2021
https://doi.org/10.5194/ejm-33-659-2021© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

3+
Zinkgruvanite, Ba4Mn2+
4 Fe2 (Si2 O7 )2 (SO4 )2 O2 (OH)2 ,a new ericssonite-group mineral from the Zinkgruvan
Zn-Pb-Ag-Cu deposit, Askersund, Örebro County, Sweden
Fernando Cámara1 , Dan Holtstam2 , Nils Jansson3 , Erik Jonsson4,5 , Andreas Karlsson2 ,Jörgen Langhof2 , Jaroslaw Majka5,6 , and Anders Zetterqvist7
1 Dipartimento di Scienze della Terra “Ardito Desio”, Università degli Studi di Milano,

Via Luigi Mangiagalli 34, 20133, Milan, Italy
2 Department of Geosciences, Swedish Museum of Natural History, Box 50007, 104 05 Stockholm, Sweden
3 Department of Civil, Environmental and Natural Resources Engineering, Luleå University of Technology,

971 87 Luleå, Sweden
4 Department of Mineral Resources, Geological Survey of Sweden, Villavägen 18, 752 36 Uppsala, Sweden
5 Department of Earth Sciences, Uppsala University, Villavägen 16, 752 36 Uppsala, Sweden
6 Faculty of Geology, Geophysics and Environmental Protection, AGH University of Science and Technology,

al. Mickiewicza 30, 30-059 Kraków, Poland
7 Zetterqvist Geokonsult AB, Kvarnbacksvägen 74, 168 74 Bromma, Sweden

Correspondence: Dan Holtstam (dan.holtstam@nrm.se)
Received: 2 July 2021 – Revised: 21 September 2021 – Accepted: 25 September 2021 – Published: 4 November 2021
3+
Abstract. Zinkgruvanite, ideally Ba4 Mn2+
4 Fe2 (Si2 O7 )2 (SO4 )2 O2 (OH)2 , is a new member of the ericssonite
group, found in Ba-rich drill core samples from a sphalerite- and galena- and diopside-rich metatuffite
succession from the Zinkgruvan mine, Örebro County, Sweden. Zinkgruvanite is associated with massive baryte, barytocalcite, diopside and minor witherite, cerchiaraite-Al, and sulfide minerals. It occurs as
subhedral to euhedral flattened and elongated crystals up to 4 mm. It is almost black and semi-opaquewith a dark-brown streak. The lustre is vitreous to sub-adamantine on crystal faces and resinous on
fractures. The mineral is brittle with an uneven fracture. VHN100 = 539, and HMohs ≈ 4.5. In thin fragments, it is reddish-black, translucent and optically biaxial (+), 2Vz > 70◦ . Pleochroism is strong anddeep brown-red (E ⊥ {001} cleavage) to olive-pale-brown. Chemical point analyses by WDS-EPMA(wavelength-dispersive X-ray spectroscopy electron probe microanalyser) together with iron valencies determined from Mössbauer spectroscopy yielded the empirical formula (based on 26 O+OH+F+Cl anions):
3+
3+(Ba4.02 Na0.03 )64.05 (Mn1.79 Fe2+
1.56 Fe0.42 Mg0.14 Ca0.10 Ni0.01 Zn0.01 )64.03 (Fe1.74 Ti0.20 Al0.06 )62.00 Si4 (S1.61 Si0.32
P0.07 )61.99 O24 (OH1.63 Cl0.29 F0.08 )62.00 . The mineral is triclinic, in space group P 1̄, with unit-cell parameters
a = 5.3982(1) Å, b = 7.0237(1) Å, c = 14.8108(4) Å, α = 98.256(2)◦ , β = 93.379(2)◦ , γ = 89.985(2)◦ and V =554.75(2) Å3 for Z = 1. The eight strongest X-ray powder diffraction lines are the following (d Å (I %; hkl)):
3.508 (70; 103), 2.980(70; 114), 2.814 (68; 122), 2.777 (70; 121), 2.699 (714; 200), 2.680 (68; 201), 2.125(100; 124, 204) and 2.107 (96; 221). The crystal structure (R1 = 0.0379 for 3204 reflections) is an array ofTS (titanium silicate) blocks alternating with intermediate blocks. The TS blocks consist of HOH sheets (Hfor heteropolyhedral and O for octahedral) parallel to (001). In the O sheet, the Mn2+ -dominant M O (1,2,3)
3+
HP
sites give ideally Mn2+
4 pfu (per formula unit). In the H sheet, the Fe -dominant M sites and A (1) sites
3+give ideally Fe2 Ba2 pfu. In the intermediate block, SO4 oxyanions and 11 coordinated Ba atoms give ideally
2× SO4 Ba pfu. Zinkgruvanite is related to ericssonite and ferroericssonite in having the same topology andtype of linkage of layers in the TS block. Zinkgruvanite is also closely compositionally related to yoshimuraite,
Ba4 Mn4 Ti2 (Si2 O7 )2 (PO4 )2 O2 (OH)2 , via the coupled heterovalent substitution 2 Ti4+ + 2 (PO4 )3− →2 Fe3+ +Published by Copernicus Publications on behalf of the European mineralogical societies DMG, SEM, SIMP & SFMC.

660

F. Cámara et al.: Zinkgruvanite, a new ericssonite-group mineral
2 (SO4 )2− but presents a different type of linkage. The new mineral probably formed during a late stage of regional metamorphism of a Ba-enriched, syngenetic protolith, involving locally generated oxidized fluids of highsalinity.

1

Introduction

The ericssonite group of minerals (Sokolova etal., 2018) comprises two members: ericssonite,
BaMn2 Fe3+ (Si2 O7 )O(OH),andferroericssonite,
BaFe2+ Fe3+ (Si2 O7 )O(OH), and two polytypes (orthorhombic and monoclinic, respectively). In both structures, an
HOH block is the main structural unit, with Mn2+ and Fe2+
being the dominant cations in the O (octahedral) sheet of
the HOH block (or TS block) and Fe3+ being the dominantcation at the [5]-coordinated sites along with Si2 O7 groupsof the H (heteropolyhedral) sheets. Ericssonite-group minerals have similar chemical properties (Ba sorosilicate) and areclosely related to seidozerite-supergroup minerals (Sokolova
and Cámara, 2017), which encompasses about 50 mineral
species and polytypes, all characterized by TS (titanium
silicate) blocks in the structural framework. Specifically, theericssonite-group minerals are close to the bafertisite (withtwo Ti atoms per formula unit, apfu) and lamprophyllite(three Ti apfu) groups. The main difference in structure
topology is the connection of octahedral and heteropolyhedral layers. Herein we describe a new mineral, zinkgru3+
vanite, ideally Ba4 Mn2+
4 Fe2 (Si2 O7 )2 (SO4 )2 O2 (OH)2 ,which is a nominally Ti-free species closely related
toyoshimuraite,
Ba4 Mn4 Ti2 (Si2 O7 )2 (PO4 )2 O2 (OH)2(abafertisite-groupmineral)andinnelite-1A
Ba4 (Na2 M 2+ Ti)Ti2 (Si2 O7 )2 [(SO4 )(PO4 )]O3 (OH)(with
M 2+ = Mn, Fe2+ , Mg, Ca; a lamprophyllite-group mineral).
The discovery of zinkgruvanite confirms the basis for aseparate classification of the ericssonite-group minerals
due to the bonding requirements of the Fe3+ O5 polyhedron(cf. Sokolova and Cámara, 2014). The mineral association
described here is unique, and members of the Ba-Cl-bearing
cerchiaraite group (cf. Kampf et al., 2013) are also reported
from Sweden for the first time.
The name of the mineral is given for the discovery locality, the Zinkgruvan mine, near Åmmeberg, municipalityof Askersund, Örebro County, Sweden (58◦ 490 N, 15◦ 60 E;
170 m a.s.l.). The new mineral and mineral name have been
approved by the Commission on New Minerals, Nomenclature and Classification, International Mineralogical Association (IMA2020-31). Type material (an incomplete drill coreslice about 10 mm thick) is deposited in the type mineral collection of the Department of Geosciences, Swedish Museumof Natural History, Box 50007, 10405 Stockholm, Sweden,
under catalogue number GEO-NRM 20170502.

Eur. J. Mineral., 33, 659–673, 2021

2

Occurrence

The Palaeoproterozoic Zinkgruvan Zn-Pb-Ag-Cu deposit is ametamorphosed sulfide ore body which has been mined continuously since 1857, with nearby deposits worked at least as
early as the 18th century (Tegengren, 1924; Haugard, 1944;
Waldén, 1957). Stratiform sphalerite- and galena-dominatedmineralization occurs here in a succession of interbedded
metatuffite, marble and skarn (Hedström et al., 1989; Jansson et al., 2017). The host succession was deposited at ca.
1.89 Ga and overprinted by polyphase metamorphism andductile deformation at ca. 1.87–1.86 and 1.84–1.80 Ga during the Svecokarelian orogeny (Stephens and Jansson, 2020).
Peak metamorphic conditions are constrained to 750 ± 50 ◦ C
and 0.4–0.6 GPa in the area (Andersson et al., 1992; Gunn,
2002; Stephens et al., 2009). The stratiform sphalerite andgalena mineralization has been heavily modified by deformation and metamorphism, including by recrystallization, by remobilization and locally by intrusion of partial melts formedby migmatization of pelitic rocks in the succession. Nevertheless, a syngenetic-exhalative origin has been suggested
for the stratiform mineralization in most studies (Hedström
et al., 1989; Allen et al., 1996; Jansson et al., 2017). Subordinate stratabound, dolomite-marble-hosted Cu-Zn mineralization occurs in the stratigraphic footwall in a vent-proximal
position and is currently mined for Cu.
Zinkgruvanite was first noted by one of the authors (Nils
Jansson) in two petrographic sections of drill core (fromca. 530 m depth) collected in conjunction with a research
project (Jansson et al., 2017). The sampling was guided byearlier observations by Anders Zetterqvist, who had previously logged the core for Zinkgruvan Mining AB and noted
an unusual Ba enrichment and an atypical mineral assemblage (Fig. 1). The core was drilled to explore the continuation of the stratiform Burkland Zn-Pb-Ag ore body at depth
and intersects the mineralized zone at about the 1500 m levelin the mine, in a proximal setting relative to an interpreted,fossil hydrothermal feeder zone (Jansson et al., 2017). The
Ba-rich zone consists of massive baryte; radial, platy barytocalcite and minor witherite; cerchiaraite-Al; and sulfide minerals in a succession of sphalerite- and galena- and diopsiderich metatuffite and is in contact with a high-grade sphaleriteand galena-rich mineralization at both sides. This abundanceof Ba is unusual for the deposit, in which Ba-bearing minerals are generally rare in the ore zone (Jansson et al., 2017).
Zinkgruvanite is found associated with barytocalcite,
diopside, baryte, cerchiaraite-Al, cerchiaraite-Fe, witherite,
galena, sphalerite, cubanite, chalcopyrite, pyrrhotite, pyrite
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F. Cámara et al.: Zinkgruvanite, a new ericssonite-group mineral

661

Figure 2. Zinkgruvanite crystals in the type specimen. Field of viewis 8 × 5 mm. Catalogue number GEO-NRM 20170502. Photo: Torbjörn Lorin.

3

Figure 1. Drill core log section from the Zinkgruvan mine showing
the position of the discovery location for the zinkgruvanite-bearing
assemblage (yellow star). MVU: metavolcanic unit.

and zhangpeishanite. It locally occurs along grain boundaries of ferroan diopside crystals, partly intergrown withthin, elongated, locally parallel to sometimes fan-like aggregates of fibrous-to-acicular or fine-grained dustings ofcerchiaraite-Al or in contact with sphalerite or as isolatedeuhedral-to-subhedral crystals and aggregates associatedwith baryte, barytocalcite and witherite (Fig. 2). Zinkgruvanite locally occurs overgrown by sulfides, specifically sphalerite. The cerchiaraite (sensu lato; s.l.) occurs in part asseemingly interstitial infillings between platy, parallel-toradiating crystals of barytocalcite and baryte. Locally, textures suggest that cerchiaraite (s.l.) formed as a partial replacement of zinkgruvanite.
Two slightly different assemblages of zinkgruvanite havebeen observed in close vicinity to each other in the drill core.
The first type is fine-grained and hosts quite abundant cerchiaraite (s.l.), both as very fine-grained masses and intergrowths or dustings and as discrete minute crystals, whereas
the other type contains little or no cerchiaraite (s.l.) and ismarkedly coarser-grained.

https://doi.org/10.5194/ejm-33-659-2021

Physical and optical properties

Zinkgruvanite occurs as subhedral-to-euhedral crystals up to
4 mm, with a platy habit, commonly flattened on {001} andelongated along [100], both as single crystals and in rare radiating aggregates. It is black, semi-opaque to reddish-blackand translucent in thin fragments, with a dark-brown streak.
The lustre is vitreous to sub-adamantine on crystal faces andresinous on fractures.
Zinkgruvanite shows perfect {001} and good {110} cleavages. The mineral is brittle with an uneven fracture. The density was not measured because of safety regulations concerning the heaviest liquids. A calculated value is 4.42(1) g/cm3
based on the empirical formula and unit-cell volume obtained
from single crystal XRD (X-ray diffraction) data. The hardness (Mohs) is estimated at 4–5 from scratch tests. Values
obtained from micro-indentation (VHN100 ) measurements,
on a randomly oriented grain available in a polished section, using a Shimadzu M-type tester are 488–616 (n = 10,
average 539), corresponding to ca. 4.5 Mohs. Pyramid indentations were straight to slightly convex; radial fractures
were frequently observed, corresponding to the “star radial”
and “simple shell” patterns, according to the terminology ofYoung and Millman (1964). The mineral is slowly soluble in
30 % HCl at room temperature, leaving a yellow solution anda white residue. Crystals are not attracted by a neodymium
hand magnet.
Zinkgruvanite is transparent in thin section, with a biaxial(+) optical character, 2Vz > 70◦ . The dispersion is strong,r > v. It exhibits a strong pleochroism in plane-polarized
light, from deep brown-red (E ⊥ {001} cleavage) to olivepale-brown (Fig. 3). Refractive indices were not determined
directly, due to the strong absorption of the crystals and values close to the highest reference liquid available (1.80). The
calculated overall n is 1.79 from Gladstone–Dale constants(Mandarino, 1981).
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662

F. Cámara et al.: Zinkgruvanite, a new ericssonite-group mineral
Table 1. Reflectance values (%) measured in air (COM – Commission on Ore Mineralogy – wavelengths in italics).

4.2

Figure 3. A zinkgruvanite crystal with baryte, barytocalcite andwitherite. Thin section (30 µm), in transmitted polarized light,
showing maximum pleochroism colours for 90◦ orientations.

4
4.1

Spectroscopic data
Reflectance

Polarized reflectance spectra were measured in air with an
AVASPEC-ULS2048x16 spectrometer attached to a Zeiss
Axiotron UV microscope (10x/0.20 Ultrafluar objective), using a halogen lamp (100 W) and a SiC (Zeiss no. 846) standard, with a circular measurement field ca. 100 µm in diameter. Results obtained in the 400–700 nm range (average of
600 scans, 100 ms integration time) are given in Table 1. The
dispersion of the reflectance is normal, and the mineral isvery weakly bireflectant.

Eur. J. Mineral., 33, 659–673, 2021

λ (nm)R2

R1

λ (nm)

R2

R1

400
420
440
460
470
480
500
520
540
546

8.74
8.46
8.41
8.25
8.21
8.12
8.05
7.97
7.92
7.98

8.53
8.25
8.20
8.03
8.07
7.96
7.86
7.82
7.78
7.79

560
580
589
600
620
640
650
660
680
700

7.97
7.87
7.87
7.86
7.74
7.81
7.80
7.74
7.76
7.79

7.77
7.67
7.68
7.69
7.67
7.68
7.65
7.65
7.64
7.65

Raman

A Raman spectrum of zinkgruvanite (Fig. 4) was collectedfrom a randomly oriented crystal on a LabRAM HR 800
micro-spectrometer, using a 514 nm Ar-ion laser source
at 1 mW power, a Peltier-cooled (−70 ◦ C) CCD (chargecoupled device) detector (Synapse), an Olympus ULWD MS
Plan 80x/0.75 na objective and a laser spot of 3 µm. Spectral positions were corrected against the Raman band at
464 cm−1 of pure quartz. The spectral resolution is about
1 cm−1 . Instrument control and data acquisition were madewith the LabSpec 5 software. No laser-induced degradationof the mineral was observed. In the spectrum obtained, twobands related to O-H stretching vibrations of OH− groups
can be identified at 3655 and 3540 cm−1 . The strong bandat 988 cm−1 is related to stretching vibration modes of the
SO4 groups, and the one at 887 cm−1 band is attributed tostretching of Si-O bonds. The band at 569 cm−1 and thestrong band at 663 cm−1 are mainly due to O-Si-O bending
vibrations. Overlapping of the latter band with a weak bandof SO4 bending vibrations having a close frequency is very
likely (e.g. for IR band assignment; Chukanov and Chervonnyi, 2016). The weaker bands at lower wavenumbers (450 to
300 cm−1 ) could be attributed to both (Mn,Fe)-O stretchingmodes and Si-O-Si bending vibrations, as well as resonancemodes involving both kinds of vibrations, whereas bands atlowest frequencies are due to lattice vibrations.
4.3

Mössbauer

A 57 Fe transmission Mössbauer spectrum (Fig. 5) was
obtained from a 5 mg powder absorber using a standard
57 Co(Rh) γ -radiation source (nominally 1.8 GBq). Twomirror image spectra (±4.28 mm/s) were collected at 54.7◦
geometry to avoid texture effects, during 100 h over 1024
channels, and calibrated against an α-iron foil. The baselineof the resulting folded spectrum was at ca. 1.42×107 counts.
Fitting and analysis were done with the MossA software(Prescher et al., 2012) assuming Lorentzian line shapes. An
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F. Cámara et al.: Zinkgruvanite, a new ericssonite-group mineral

663

Figure 4. Raman spectrum of zinkgruvanite.

absorption doublet (A; see Fig. 5) with centroid shift (CS)= 0.34(2) and quadrupole splitting (QS) = 0.32(2) mm/s is
ascribed to Fe3+ in [5]-coordination by O, in analogy withdata for ericssonite (Hålenius, 1995). Note that a minor contribution from [6]-coordinated Fe3+ that must be present according to structural data (see Sect. 7) is not well resolvedin the spectrum. A pair of doublets (B and C in Fig. 5), constrained to have the same CS (= 1.14(2) mm/s), were used
to fit the remaining absorption, with QSB = 2.30(10) and
QSC = 1.95(10) mm/s, respectively. These values are consistent with Fe2+ (high spin) in [6]-coordination with O andvery close to what was previously found in bafertisite-groupminerals (Holtstam, 1998; Sokolova et al., 2009; Zhitova etal., 2017). Ideally, three doublets related to Fe2+ -enrichedsites could be anticipated in the zinkgruvanite spectrum, but
only two are distinguishable, probably due to the small differences in geometry of the corresponding coordination polyhedra. From area ratios, the fraction of Fe2+ is 42(10) % of
total Fe. Full width at half maximum was in the range of 0.3–
0.4 mm/s for the three doublets. The final χ 2 value was 0.8.

5Chemical composition

The chemical composition was determined using an electronprobe microanalyser (EPMA), a JXA-8530F JEOL Superprobe. Raw data were corrected using the PAP procedure(Pouchou and Pichoir, 1984). The instrument settings were
15 kV acceleration voltage, 10 nA beam current and 3 µm
beam diameter. The number of point analyses was 30, collected from two grains. Reference materials, measured lines
and analytical results are reported in Table 2. Strontium was
below the detection limit in all point analyses. The H2 O concentration was not determined directly because of dearth ofmaterial. The presence of CO2 is indicated neither by crystal structure refinement nor by spectroscopic data. Analytical
data for selected associated Ba minerals are given in Table 3.
https://doi.org/10.5194/ejm-33-659-2021

Figure 5. Mössbauer (57 Fe) spectrum of zinkgruvanite. See text for
assignment of the three subspectra A, B and C.

The empirical formula calculated on the basis of
26 anions (O+OH+F+Cl), accounting for known
structural features (see below) and the iron valence determined from Mössbauer spectroscopy, is
3+(Ba4.02 Na0.03 )64.05 (Mn1.79 Fe2+
1.56 Fe0.42 Mg0.14 Ca0.10 Ni0.01
3+
Zn0.01 )64.03 (Fe1.74 Ti0.20 Al0.06 )62.00 Si4 (S1.61 Si0.32 P0.07 )61.99
O24 (OH1.63 Cl0.29 F0.08 )62.00 for crystal no. 1 (Table 2). The
simplified formula is Ba4 (Mn,Fe2+ )4 (Fe3+ ,Ti)2 (Si2 O7 )2[(S,Si,P)O4 ]2 O2 (OH,Cl)2 , and the ideal formula is3+
Ba4 Mn2+
4 Fe2 (Si2 O7 )2 (SO4 )2 O2 (OH)2 , which requires
BaO 41.58, MnO 19.23, Fe2 O3 10.83, SiO2 16.29, SO3
10.85 and H2 O 1.22 for a total 100 wt %. Although thisformula could be reduced by a factor of 2, it is kept in thisway, with Z = 1, to emphasize the close relation to theseidozerite-supergroup minerals.

6

X-ray crystallography

Powder X-ray diffraction data were collected with a Panalytical X’Pert3 powder diffractometer equipped with an
X’Celerator silicon-strip detector and operated at 40 mA and
45 kV (Cu Kα radiation, λ = 1.5406 Å). Bragg peak positions (Table 4) were determined with the Panalytical HighScore Plus 4.6 software and corrected against an external
Si standard (NBS 640b; National Bureau of Standards).
The triclinic (P 1̄) unit-cell parameters refined by the leastsquares method from the powder data are a = 5.3989(6) Å,b = 7.0319(8) Å, c = 14.821(2) Å, α = 98.274(11)◦ , β =93.436(12)◦ , γ = 90.087(10)◦ and V = 555.77(9) Å3 for
Z = 1.
A single-crystal X-ray study was done on a crystal fragment (0.050 × 0.125 × 0.190 mm) with a Rigaku XtaLAB
Synergy with a hybrid pixel array detector, with graphitemonochromatized MoKα radiation (λ = 0.71073 Å); workEur. J. Mineral., 33, 659–673, 2021

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F. Cámara et al.: Zinkgruvanite, a new ericssonite-group mineral

Table 2. Chemical data (in wt %) for zinkgruvanite.
Constituent

Crystal no. 1
n = 15

Crystal no. 2
n = 15EPMA reference material

Mean

2σ

Mean

2σ

SiO2
TiO2
Al2 O3Cr2 O3[FeO]
FeOa
Fe2 O3 a
MnO
ZnO
NiO
V2 O5
P2 O5
MgO
CaO
Na2 O
K2 O
BaO
F
Cl
SO3
H2 Ob
O ≡ Cl, F

17.38
1.05
0.20
0.01
17.94
7.53
11.56
8.49
0.03
0.03
0.03
0.31
0.37
0.39
0.07
0.01
41.26
0.10
0.70
8.63
0.99
−0.20

0.34
0.12
0.06
0.04
0.44

17.47
1.21
0.22
0.01
18.36
7.71
11.84
7.70
0.04
0.02
0.03
0.96
0.38
0.36
0.06
0.01
41.29
0.04
0.60
8.00
1.01
−0.17

0.32
0.25
0.07
0.04
0.47

(Kα, TAP) – wollastonite(Kα, PET) – pyrophanite(Kα, TAP) – Al2 O3(Kα, LIF) – Cr2 O3(Kα, LIF) – fayalite

0.27
0.08
0.07
0.04
0.70
0.07
0.12
0.10
0.02
0.40
0.14
0.12
0.92

(Kα, LIF) – pyrophanite(Kα, LIF) – ZnO(Kα, LIF) – NiO(Kα, LIF) – vanadinite(Kα, PET) – apatite(Kα, TAP) – MgO(Kα, PET) – wollastonite(Kα, TAP) – albite(Kα, PET) – orthoclase(Lα, PET) – baryte(Kα, LDE1) – apatite(Kα, PET) – apatite(Kα, PET) – baryte

Total

98.93

0.32
0.08
0.06
0.06
0.28
0.06
0.06
0.08
0.02
0.36
0.16
0.06
0.32

98.79

a Based on Mössbauer spectroscopy. b Calculated from structure (OH+F+Cl) = 2.

ing conditions were 50 kV and 1 mA, and the detector-tosample distance was 6.2 cm. A combination of ω and φ scans,with a step scan of 0.5◦ and exposure time of 2 s per frame
were used to maximize redundancy and data coverage.
The crystal structure was solved by direct methods andrefined to R1 = 0.032 in SHELXTL (Sheldrick, 2015) using neutral-atom scattering curves from the International Tables (Wilson, 1992). Experimental details, unit-cell parameters and R indices are given in Table 5. Fractional atom
coordinates, site occupancies and isotropic-displacement parameters are reported in Table 6. Bond distances are given in
Table 7. A crystallographic information file (CIF) containing
observed structure factors has been deposited as the Supplement.
The crystal structure of zinkgruvanite contains an HOH
layer (see Sokolova and Cámara, 2017, for nomenclature) as
the main structural unit (Fig. 6a). The dominant cations in thecentral O (octahedral) sheet of the HOH layer are Mn2+ andFe2+ ; they are distributed over three octahedral sites (M(1),M(2) and M(3)); the two adjacent H sheets are composed of[5]-coordinated Fe3+ polyhedra M H and Si2 O7 groups (Si(1)and Si(2) sites). Between the HOH layers, there is a distorted
layer of Ba atoms at two cation sites, AP (1) and B P , on the
periphery of the HOH layer, and a TS block. The AP (1) andEur. J. Mineral., 33, 659–673, 2021

B P sites coordinate (SO4 ) and configure the I block (intermediate block, in the sense of Sokolova, 2006). At converO sites. The
gence, a split model was applied to the AP and XA
latter was interpreted as resulting from partial occupancy by
Cl in agreement with the chemical analysis (Table 2). It was
not possible to locate the position of H atoms in the difference Fourier maps, probably due to the split site related toCl.

7Discussion

7.1
7.1.1

Crystal structure and crystal chemistry
Cation sites

In the heteropolyhedral sheet, tetrahedral sites are occupied
solely by Si in zinkgruvanite, as confirmed by the averageobserved bond lengths (1.620–1.624 Å, Table 7). The M H
sites are dominantly occupied by Fe3+ with minor Ti and
Al (Ti0.20 Al0.06 ), and the observed average bond length is
1.964 Å, larger than that in yoshimuraite (1.923 Å), where it
is dominantly occupied by Ti (0.78 apfu), and minor Fe3+
(0.22 apfu) (McDonald et al., 2000). The calculated site scathttps://doi.org/10.5194/ejm-33-659-2021

F. Cámara et al.: Zinkgruvanite, a new ericssonite-group mineral
Table 3. Composition (in wt %) of barium-bearing minerals associated with zinkgruvanite.
Cerchiaraite-Aln = 10

Barytocalcite
n = 11Witherite
n=8

Mean

σ

Mean

σ

Mean

σ

25.34
0.61
10.23
0.01
0.02
0.10
0.05
44.27
–
6.85
0.71
0.01
0.12
0.00
6.52
0.01

0.38
0.06
0.68
0.02
0.03
0.05
0.02
0.77
–
0.82
0.10
0.01
0.06
0.00
0.12
0.02

–
–
–
–
–
–
19.06
50.40
0.18
0.03
–
–
–
–
–
–
29.60

–
–
–
–
–
–
0.17
0.46
0.17
0.03
–
–
–
–
–
–

–
–
–
–
–
–
0.69
76.68
0.58
0.04
–
–
–
–
–
–
22.30

–
–
–
–
–
–
0.07
0.59
0.16
0.05
–
–
–
–
–
–

SiO2
TiO2
Al2 O3
V2 O3
Cr2 O3
MgO
CaO
BaO
SrO
Fe2 O3
MnO
NiO
Na2 O
K2 O
Cl
SO3
CO2calc
H2 Ocalc
O ≡ Cl

4.90
−1.47

Total

98.29

99.27

100.29tering values agree well with the site scattering obtained bystructure refinement (Table 8).
There are four M O [6]-coordinated sites in the O sheet:
M(1), two M(2) and M(3). These are occupied dominantly
by Mn2+ , although Fe2+ is also very abundant. The M(1)and M(2) polyhedra are slightly smaller (and probably hostminor Fe3+ ), whereas the M(3) polyhedron is larger, and weassume that it hosts some Ca, which is coupled to the replaceO site. The same trend in polyment of (OH) by Cl at the XA
hedron size occurs in yoshimuraite (M(1) ≈ M(2) < M(3);McDonald et al., 2000), with larger average bond distances
because of the higher Mn2+ content. Average bond distancesin zinkgruvanite (Table 7) and the observed bond valencesums (Table 6) agree with dominance of Mn2+ at the M O
sites. Agreement between aggregated observed site scattering and calculated site scattering from the assigned site population is close (97.2 vs. 100.1 epfu; electrons per formulaunit).
There are two types of peripheral sites: the AP sites thatare closer to the TS block and the B P sites, which are partof the intermediate layer along with oxyanions (in this casethe SO4 groups). The AP sites are split into two sites: AP (1)(occupied by Ba, 1 apfu) and AP (2), a satellite peak due toOminor Na (0.03 apfu; Table 1) being bonded to F at the XAanion site (0.08 apfu) close to the O sheet, whereas Ba at theAP (1) is further from the O sheet to avoid steric hindrance
O anion site (AP (1)–with the H associated with OH at the XA
https://doi.org/10.5194/ejm-33-659-2021

665

Table 4. Powder X-ray diffraction data (d in Å) for zinkgruvanite.
I

Icalc

dobs

dcalc

h

k

l

53
32
26
30
35
42
70

47
32
47
47
32
78
44
48
21
83
68
40
70
35
60
75
92
43
74
20
11
13
32
28
26
27
26
17
21
17
18
15
40
10
9
11

4.875
4.231
4.163
3.908
3.730
3.632
3.508

4.880
4.228
4.155
3.906
3.732
3.632
3.512
3.497
3.440
3.334
3.156
3.117
2.97752.92982.83942.81302.77332.69452.67912.57992.48022.41872.23572.2053
2.17192.12712.1242
2.10952.10632.0776
1.9872
1.84261.75741.65401.5933
1.4683

0
1
1
1
1
1
1
0
1
0
1
1
1
1
1
1
1
2
2
2
2
0
2
0
1
2
1
2
2
2
1
0
0
3
3
2

0
1
1
1
0
1
0
2
1
2
1
0
1
2
1
2
2
0
0
0
0
2
0
1
2
2
2
0
2
2
2
3
4
1
2
4

3
1
1
2
3
2
3
1
3
2
3
4
4
1
4
2
1
0
1
2
2
5
4
6
5
1
4
4
1
2
5
4
1
3
2
0

51
56
48
56
70
61
61
68
70
71
85
40
16
15
45
25
31
100
96
58
32
21
49
29
42
29

3.445
3.330
3.154
3.108
2.97992.92752.84012.81362.77712.69902.68042.57822.47822.42002.23652.20902.17092.12502.10712.0755
1.98761.8403
1.75701.65371.5926
1.4695O = 3.57 Å). This could explain the rather short stretchXA
ing frequencies for (OH− ) in the Raman spectrum (3655
and 3540 cm−1 ). The presence of two different Raman shifts
must be ascribed to the dominant Mn2+ and Fe2+ at the twoM(2) and the M(1) sites, i.e. Mn2+ and Fe2+ . Mean bondlengths are compatible with Ba at the AP (1) site, and Na is
O ). The B P site is fullyat the AP (2) site (coordinating Cl at XA
occupied by Ba, as shown by the observed site scattering andmean bond lengths (Table 6).
In the intermediate block, Ba and SO4 form a baryte-likelayer parallel to (010) (Fig. 7a and b). The overall geometryis the same as in baryte, although some distortion is present
to adapt to bonding to the oxygens of the Si2 O7 and Fe3+ O5groups of the H sheet. The S-S distances in the intermediate
block of zinkgruvanite are 4.015 and 5.313 Å, whereas theEur. J. Mineral., 33, 659–673, 2021

666

F. Cámara et al.: Zinkgruvanite, a new ericssonite-group mineral

Table 5. Crystal data and experimental conditions for the single-crystal XRD study.
Temperature
Wavelength
Crystal system
Space group
Unit-cell dimensions

Unit-cell volume
Z
Absorption coefficientF (000)
Theta range for data collection
Index ranges
Reflections collected
Independent reflections
Completeness to θ = 30.03◦
Refinement method
Data/restraints/parameters
Goodness of fit on F 2Final R indices [I > 2σ (I )]R indices (all data)
Largest diff. peak and hole293(2) K
0.71073 Å
Triclinic
P1
a = 5.39820(10) Å, α = 98.256(2)◦ .
b = 7.02370(10) Å, β = 93.379(2)◦ .
c = 14.8108(4) Å, γ = 89.985(2)◦ .
554.75(2) Å3
1
11.140 mm−1666
3.78 to 30.03◦ .
−7≤ h ≤ 7, −9 ≤ k ≤ 9, −20 ≤ l ≤ 20
14 7683204 (Rint = 0.0499)
98.5 %
Full-matrix least-squares on F 2
3204/0/209
1.030
R1 = 0.0323, wR 2 = 0.0758
R1 = 0.0379, wR 2 = 0.0787
1.751 and −1.361 e.Å−3

corresponding values for baryte are 4.002 and 5.000 Å (using the atom coordinates of Jacobsen et al., 1998). The mean
S-O bond length is 1.471 Å, which agrees well with a site
dominantly occupied by S. A similar average bond length
was reported for yoshimuraite (1.487 Å) by McDonald et al.
(2000) for an S-site occupancy of (P0.46 S0.34 Si0.17 )60.97 andan incident bond valence of 5.5 v.u. (Table 5 of McDonald
et al., 2000; valence unit). Incident bond valence calculatedwith full occupancy yields values too high at O(6) and O(7)but good values for O(1) and O(13) that show bond valence
deficiency.
7.1.2

Anion sites

There are 13 anion sites in the structure of zinkgruvanite,
12 of which are fully occupied by O2− , as indicated by the
O bonds to two M(2)incident bond valence (Table 6). The XA
and one M(3) cations, and its incident bond valence (Table 6)
O must host a monovalent anion, dominantly
indicates that XA−(OH ) substituted by minor F or Cl. The O(13) site bonds
to the cations at the S and B P sites and shows a prominentbond valence deficiency and high Ueq (Table 6 and Fig. 6a)that is related to the heterovalent substitutions at the S sites(S6+ substituted by P5+ and Si4+ ). The O(1) site also showsa high equivalent isotropic-displacement factor (Table 6) andis also bonded to cations at the S, B P and AP sites. Alsoin this case, the high displacement parameters are likely due
to static disorder to be ascribed to heterovalent substitutions
at the S site. Bond valence has been calculated assuming an
occupancy of 0.87 S atoms per site. Full occupancy by S inEur. J. Mineral., 33, 659–673, 2021

creases incident bond valence at O(1) and O(13) to values
closer to 2 v.u., but values at O(6) and O(7) become too high(2.14 and 2.12 v.u., respectively). This indicates that full occupancy of the S site by sulfur requires smaller cations at AP
and B P . Therefore, heterovalent substitution of S by P (or Si)
is favoured.
7.1.3

Nomenclature and classification

Zinkgruvanite is a member of the ericssonite groupand is strongly related to ericssonite and ferroericssonite by the insertion of SO4 groups at the I blockand by the substitutions of Mn2+ by Fe2+ at the O
sheet in ferroericssonite. It is closely related to theminerals of the seidozerite supergroup, specificallyto yoshimuraite, Ba4 Mn4 Ti2 (Si2 O7 )2 (PO4 )2 O2 (OH)2 ,via the coupled heterovalent substitution 2 Ti4+ + 2(PO4 )3− → 2 Fe3+ + 2 (SO4 )2− , and innelite-1A,
Ba4 Ti2 (Na2 M 2+ Ti)(Si2 O7 )2 [(SO4 )(PO4 )]O2 [O(OH)],via
theadditional
coupledheterovalent
subO
O
stitution(SO4 )2− +M (Na2 Ti)6+ +XA O2−→
O
6+ + XO
A OH− .
(PO4 )3− +M (Mn2+)
3
In yoshimuraite there is a topological change accompanying this substitution, as discussed by Sokolova and Cámara (2014), that it is related to the linkage of H sheets to
the O sheet in the TS block. The differences in linkage in the
TS block between these two minerals are clearly visible inFig. 6. The HOH layer in which the M H sites are occupied
by Fe3+ = 2 apfu (Fig. 6a, zinkgruvanite, and Fig. 8, ferroericssonite) has linkage 1 (in the sense of Sokolova, 2006): two
https://doi.org/10.5194/ejm-33-659-2021

F. Cámara et al.: Zinkgruvanite, a new ericssonite-group mineral

667

Table 6. Atom coordinates and equivalent isotropic displacement parameters (Å2 ) for zinkgruvanite. Ueq is defined as one-third of the traceof the orthogonalized U ij tensor.
Site and ref. s.c.∗
B P BaAP (1) Ba
AP (2) Ba
M H FeM(1) Fe
M(2) Fe
M(3) Fe
Si(1) Si
Si(2) Si
S
O(1)
O(2)
O(3)
O(4)
O(5)
O(6)
O(7)
O(8)
O(9)
O(10)
O
XA(OH)O
XA(Cl)
O(12)
O(13)

x

y

z

Ueq

s.o.f.

B.V.

1.23102(5)0.71960(6)0.721(4)−0.29776(12)00.49965(13)00.1992(2)0.1984(2)1.2468(3)1.2639(8)−0.0383(6)0.4541(6)−0.0395(6)0.4531(6)1.4635(7)1.0199(7)0.1782(6)−0.3156(6)0.2025(7)0.327(2)0.324(3)0.1796(6)1.2390(11)1.12167(4)0.58658(4)0.569(3)0.05864(9)1/20.76557(11)1/2
0.78356(16)0.32982(16)0.6968(2)0.7150(7)0.2617(5)0.8791(5)0.8792(5)0.2615(5)0.7978(6)0.7983(6)0.2737(5)0.0204(5)0.5643(5)0.4823(18)0.469(2)0.7766(5)0.5045(7)0.883149(19)0.81206(4)0.770(3)0.69843(5)1/20.50054(5)1/20.68739(8)0.68489(8)0.97635(10)1.0777(3)0.7335(2)0.7362(2)0.7368(2)0.7327(2)0.9483(3)0.9488(3)0.5749(2)0.5721(2)0.7135(3)0.4322(7)0.4018(7)0.5773(2)0.9278(5)0.01622(11)0.01783(15)0.021
0.0119(2)0.0130(3)0.0161(3)0.0159(4)0.0101(3)0.0102(3)0.0187(5)0.0323(10)0.0144(7)0.0155(7)0.0148(7)0.0157(7)0.0256(8)0.0254(8)0.0153(7)0.0150(7)0.0209(8)0.0236(16)0.0236(16)0.0149(7)0.0474(16)0.989(4)0.985(5)0.016(2)0.983(5)0.483(3)0.922(3)0.466(3)1
10.874(8)
1
1
1
1
1
1
1
1
1
1
0.77(1)0.23(1)
10.874(8)

2.253
2.061
0.033
2.862
2.102
1.961
2.048
4.001
4.043
5.250
1.850
2.035
1.970
1.978
2.019
1.946
1.932
2.002
1.980
2.046
0.760
0.303
1.942
1.761

∗ ref. s.c.: scattering curve used for refine site occupancy. s.o.f.: site occupancy factor. B.V.: bond valence calculated with values from

Gagné and Hawthorne (2015), except for bonds involving Cl taken from Brown and Altermatt (1985), and the ideal chemical composition(except for S site at 0.87 apfu of S; see text for discussion).

Si2 O7 groups of two H sheets link to the trans edges of an octahedron of the O sheet in zinkgruvanite and ferroericssonite(Fig. 9f). Where the M H sites are occupied by Ti4+ = 2 apfu,
as in yoshimuraite (Fig. 6b), the HOH layer has linkage 2 (asin bafertisite-group minerals, where Ti(Nb) = 2 apfu): two
Si2 O7 groups of two H sheets link to two octahedra of the
O sheet adjacent along b (Fig. 9c).
The chemical composition of the O sheet for bothyoshimuraite and zinkgruvanite corresponds to thebafertisite-group minerals: only divalent cations (mostly
Mn2+ and Fe2+ , respectively) are dominant in the O sheet(Sokolova and Cámara, 2017). However, the HOH layer with
Fe3+ = 2 apfu has linkage 1, as in lamprophyllite-groupminerals where Ti = 3 apfu, e.g. in barytolamprophyllite,
ideally (BaK)Ti2 Na3 Ti(Si2 O7 )2 O2 (OH)2 , which has acompletely different chemistry of the O sheet, i.e. Ti(Nb)and Na in the O sheet instead of 4 M2+ cations. Linkage
and topology (as well as cell parameters) are very similar
to those shown by innelite-1A (Sokolova et al., 2011)
Ba4 Ti2 Na2 M2+ Ti(Si2 O7 )2 [(SO4 )(PO4 )]O2 [O(OH)] (withM2+ = Mn, Fe2+ , Mg, Ca). But again, the chemical composition of the O sheet is very different, and so are site
geometry and dimensions of polyhedra.
https://doi.org/10.5194/ejm-33-659-2021

The difference in linkage between yoshimuraite andzinkgruvanite is to be ascribed to the different bond valenceO sites coordinating cations at
incident at the anions at the XM
HO
the M and M sites as discussed by Sokolova and Cámara
(2014) (see their Fig. 2c). Longer M H -XO
M bonds occur when
this M H is occupied by Fe3+ (> 1.8 Å), therefore having a
O . Where Ti4+ (Nb5+ ) oclower bond valence incident at XM
H
Hcupies the M site, shorter M –XO
M distances are observed(< 1.8 Å), providing bond valence excess. When linkage isof type 1, there is one octahedron in the O sheet having every apex shared with a polyhedron of the H sheet, which hosthigh-charge cations. This implies that the cation at that octahedral site must be a low-charge cation and/or polyhedronsize must grow (lamprophyllite-group minerals having Na at
the O sheet) or the charge of the M H site must be lower andthe polyhedron must be larger (as in ericssonite-group minerals). Alternatively, a change in linkage that avoids having
one octahedron in the O sheet sharing every apex with a polyhedron of the H sheet can keep a higher-charge cation, as inyoshimuraite.
This difference led Sokolova et al. (2018) to propose aseparate group for ericssonite-group minerals (Fe3+ disilicates), which was approved by IMA (Memorandum 78Eur. J. Mineral., 33, 659–673, 2021

668

F. Cámara et al.: Zinkgruvanite, a new ericssonite-group mineral

Table 7. Selected interatomic distances (Å), polyhedral volumes and polyhedral distortion parameters for zinkgruvanite.
Si(1)< Si(1)V

M(1)< M(1)V

S<S
V

AP (2)< AP (2)< AP (2)−O(3)−O(12)−O(10)
−O(4)
−O>
(Å3 )
TQE
TAV (◦2 )−O(8) × 2
−O(12) × 2−O(9) × 2
−O>
(Å3 )
OQE
OAV (◦2 )1.616(4)1.621(4)1.641(4)1.618(4)1.624
2.18
1.005120.76
2.261(3)2.258(3)2.058(4)
2.192
13.59
1.0241
66.27−O(13)
−O(7)
−O(1)
−O(6)
−O>
(Å3 )
TQE
TAV (◦2 )1.435(5)1.483(4)1.485(5)1.479(4)
1.471
1.626
1.0028
11.35

−O(3)
−O(5)
−O(10)−O(4)−O(2)−O(10)
−XO
A(Cl)
−O>
O
−XA(OH)−O>

2.700(3)2.570(3)2.780(3)2.650(3)2.530(3)2.870(3)2.520(5)2.660
2.960(5)
2.724

Si(2)

< Si(2)V

M(2)< M(2)V< M(2)V

AP (1)< AP (1)−O(5)−O(10)
−O(8)
−O(2)
−O(>
(Å3 )
TQE
TAV (◦2 )O ×2−XA−O(8) × 2
−O(9) × 2
−O>
(Å3 )
OQE
OAV (◦2 )O−XA(Cl)
×2
−O>
(Å3 )
OQE
OAV (◦2 )1.614(4)1.640(4)1.617(4)1.609(4)
1.620
2.166
1.005120.50
2.272(11)2.119(4)2.178(4)
2.191
13.34
1.035
106.642.518(12)
2.264
15.18
1.019
39.78

−O(10)
−O(5)
−O(3)
−O(6)
−O(2)
−O(1)
O
−XA(Cl)−O(4)−O(10)−O(7)−O>

3.066(4)2.774(4)2.830(4)2.766(4)2.772(4)2.852(4)3.130(11)2.826(4)3.055(4)2.773(4)
2.884

MH

< MH
V
M(3)

< M(3)V< M(3)
V

BP

< BP
O
XA

O
−XA(OH)

−O(3)
−O(5)
−O(4)
−O(9)
−O(2)
−O>
(Å3 )

1.997(4)1.992(4)1.992(4)1.848(4)1.992(4)
1.964
5.856

−O(12) × 2
O ×2
−XA
−O(8)
−O>
(Å3 )
OQE
OAV (◦2 )O−XA(Cl)
×2
−O>
(Å3 )
OQE
OAV (◦2 )2.293(3)2.077(11)2.250(3)
2.206
13.75
1.030
82.33
2.330(14)
2.291
15.68
1.015
51.62

−O(1)
−O(6)
−O(5)
−O(6)
−O(3)
−O(13)
−O(7)
−O(7)
−O(1)
−O(2)
−O(4)
−O>

2.951(5)2.895(5)2.883(3)2.858(4)2.887(3)2.675(5)2.858(4)2.888(5)2.963(5)2.870(3)2.881(3)2.874

0.446(15)∗ OQE: octahedral quadratic elongation. OAV: octahedral angle variance. TAV: tetrahedral angle variance. TQE: tetrahedral quadratic elongation in the sense of

Robinson et al. (1971).

SM/17). Zinkgruvanite is a member of the ericssonite group(Sokolova et al., 2018), similar to ericssonite (Moore, 1971)
and ferroericssonite (Kampf et al., 2011; Fig. 8), although it
contains an interlayer of SO4 that is absent in ericssonite. The
discovery of this new species confirms the model of Sokolova
and Cámara (2014).
Zinkgruvanite fits in the Strunz group 9.BE.25 (sorosilicates; Si2 O7 groups, with additional anions; cations in octahedral and greater coordination; Strunz and Nickel, 2001).
7.1.4

Compositional variations

For the material investigated here, some chemical variation3−
2−
is present. The substitution of SiO4−
4 and PO4 for SO4
4+
is coupled to variations in Ti (Fig. 10). Heterovalent subEur. J. Mineral., 33, 659–673, 2021

stitution of the oxyanion in the I block was also reported
for yoshimuraite with (P0.46 S0.34 Si0.17 )60.97 O4 (McDonald
et al., 2000). Some degree of heterovalent Ti4+ → Fe3+ substitution was reported by McDonald et al. (2000) in yoshimuraite. Since the Ti4+ → Fe3+ substitution affects the bondvalence incident at cations of the O sheet and ultimately
seems to control the topology of the crystal structure (linkage 1 in zinkgruvanite and linkage 2 in yoshimuraite), it
seems reasonable to propose that at a certain Ti4+ : Fe3+ ratio, the zinkgruvanite structure will transition to the yoshimuraite structure. In turn, the existence of intergrowths ofyoshimuraite and zinkgruvanite seems possible and should
be checked by transmission electron microscopy.

https://doi.org/10.5194/ejm-33-659-2021

2+
Mn2+
0.46 + Fe0.42 + Ca0.10 + Ni0.01 + Zn0.01
2+(Mn1.79 Fe1.56 Fe3+
0.42 Mg0.11 Ca0.10 Ni0.01 Zn0.01 )64.00

Ba1.00Ba0.97
Na0.03(Ba1.97 Na0.03 )62.00

S1.62 + Si0.32 + P0.07

24.2(2)
97.24

55.4(2)55.2(9)0.9(1)
73.75

28.0(1)Figure 6. The crystal structures of zinkgruvanite (a) and yoshimuraite (b) (McDonald et al., 2000) for comparison. Mn2+ octahedra: purple; Fe3+ O5 pyramid: light brown; Ti4+ O5 pyramid:
cyan; SiO4 tetrahedra: blue; SO4 tetrahedra: yellow; PO4 tetrahedra: pink, Ba2+ cations: cyan; oxygen anions: red; chlorine anions:grey. Obtained with Vesta 3 (Momma and Izumi, 2011).

It is noteworthy that the homovalent Mn2+ → Fe2+ substitution is also significant in zinkgruvanite (but very limited
for yoshimuraite; Watanabe et al., 1961; McDonald et al.,2000), and this suggests the possible occurrence of compositions with Fe2+ ≥ Mn2+ for zinkgruvanite (i.e. a “ferro-”
analogue). As reported for yoshimuraite from the type locality (Watanabe et al., 1961), zinkgruvanite also shows thepresence of some Cl, related to a OH → Cl substitution at theO site. The structural model of zinkgruvanite shows splitXA
O site, similar to what is observed
ting of the ions at the XA
for some Cl-bearing amphiboles (Oberti et al., 1993). This
was not reported for ferroericssonite with 0.19 Cl atoms pfu(Kampf et al., 2011).

https://doi.org/10.5194/ejm-33-659-2021[4] S[7] AP (2)[10] AP (1)[11] B P[6] M(3)[6] M(2)[6] M(1)7.2[5] M H

669

S2
1.471
31.45

Ba

Ba2
2.884
2.660
53.35
0.33
73.30

Ba
2.874
56.00

Mn2+
4 Mn2+
2.206
25.00
100.13

Mn2+
Mn2+
2.192
2.191
25.1(2)47.94(8)

2+
3+
Mn2+
0.46 + Fe0.41 + Fe0.132+2+3+
Mn0.87 + Fe0.73 + Fe0.29 + Mg0.11

25.54
49.59

2 Fe3+
1.964
50.42
51.1(3)4+Fe3+
1.74 + Ti0.20 + Al0.06< M-O>obs. (Å)
Calculated site scat. (epfu)
Assigned site population (apfu)
Refined site scattering (epfu)
Site

Table 8. Refined site scattering and assigned site populations for cation sites in zinkgruvanite.

Ideal comp. (apfu)

F. Cámara et al.: Zinkgruvanite, a new ericssonite-group mineral

Genetic aspects

The minerals of the seidozerite supergroup commonly occur
in highly differentiated magmatic complexes (peralkalineto-agpaitic rocks). The type locality of the zinkgruvaniterelated mineral yoshimuraite, the Noda-Tamagawa mine, isa metamorphosed bedded Mn deposit, in which the mineraloccurs in the border facies of an alkaline pegmatite dikecrosscutting the ores (Watanabe et al., 1961). Ericssonitegroup minerals occur in skarn assemblages within metamorEur. J. Mineral., 33, 659–673, 2021

670

F. Cámara et al.: Zinkgruvanite, a new ericssonite-group mineral

Figure 7. Comparison of the geometry of the intermediate block inzinkgruvanite (a) and a (010) slab of baryte (b). Drawn with Vesta
3 (Momma and Izumi, 2011). Baryte model from Jacobsen et al.
(1998).

Figure 8. The crystal structure of ferroericssonite (Kampf et al.,2011) for comparison. Fe2+ octahedra: light brown; Fe3+ O5 pyramid: light brown; SiO4 tetrahedra: blue; Ba2+ cations: cyan; oxygen anions: red; chlorine anions and/or OH groups: grey. Drawn
with Vesta 3 (Momma and Izumi, 2011).

Eur. J. Mineral., 33, 659–673, 2021

Figure 9. Linkage of H and O sheets in yoshimuraite: (a) the O(octahedral) sheet and the H (heteropolyhedral) sheet of (Si2 O7 ) (inblue) and M H polyhedra (in light yellow where occupied by Ti andin brown where occupied by Fe3+ ) and (b) the TS block composedof HOH sheets; in zinkgruvanite (d) O + H sheets and (e) TS block
composed of HOH sheets. M O octahedra in purple centred by Mn
and in green centred by Fe2+ . In yoshimuraite, linkage 2 occurs (c)where two Si2 O7 groups link to two octahedra of the O sheet adjacent along t2 . In zinkgruvanite (ericssonite), linkage 1 occurs (f)where two H sheets connect to the O sheet such that two Si2 O7groups on opposite sides of the O sheet link to trans edges of thesame octahedron of the O sheet.

phosed Mn ore deposits of inferred syngenetic origin (ericssonite; Moore, 1971; Matsubara and Nagashima, 1975) andin contact-metamorphosed Ba-rich sediments altered by late
fluids (ferroericssonite; Dunning et al., 2018). Zinkgruvanite
joins ericssonite through its occurrence in an originally syngenetic deposit which has been modified by regional metamorphism.
Geochemical studies by Hedström et al. (1989) and Jansson et al. (2017, 2018) demonstrated that all chemical components present in the Ba-rich associations were introduced
already during the depositional stage of the stratiform Zn-PbAg mineralization, via hydrothermal alteration of the stratigraphic footwall prior to regional metamorphism. Despite therarity of the zinkgruvanite-bearing, Ba-rich associations at
Zinkgruvan, they are not unusual with regards to the suiteof elements, only with regards to the anomalously high Ba
content and unusual mineralogy. It is suggested that thesehttps://doi.org/10.5194/ejm-33-659-2021

F. Cámara et al.: Zinkgruvanite, a new ericssonite-group mineral671

The absolute timing of formation of zinkgruvanite and associated minerals such as barytocalcite, baryte, witherite andcerchiaraite is uncertain. The relatively coarse-grained, radial or generally diverging aggregates of mostly subhedral
crystals in the form of a space-infill texture, seen in primarily barytocalcite and baryte (including interstitial infillings of cerchiaraite (s.l.)) between crystals, could be interpreted as vein- or fissure-filling assemblages formed by fluidmediated processes. Somewhat speculatively, the formationof the exotic, Ba-Cl-F-enriched assemblage could have beenconnected to a late stage of devolatilization related to e.g.
regional pressure release.

Data availability. A CIF file is deposited as the Supplement.

Supplement. The supplement related to this article is available online at: https://doi.org/10.5194/ejm-33-659-2021-supplement.

Figure 10. Compositional variations in zinkgruvanite based on
EPMA. Regression lines correspond to R 2 = 0.69 and 0.74, respectively.

Ba-rich associations could have formed via internal remobilization and enrichment of syngenetic components during
regional metamorphism or constitute a more unusual member of the pre-metamorphic alteration system, which formed
the Zinkgruvan Zn-Pb-Ag deposit.
Jansson et al. (2017) interpreted that the stratiform Zn-PbAg deposit and associated Cu mineralization formed upon
exhalation of oxidized brines into a reducing seafloor environment. From the composition of zinkgruvanite and its associated minerals, it can be inferred that the fluids responsible for their formation were saline fluids enriched in Cl and F,
as also indicated by the presence of minute grains of zhangpeishanite, BaFCl. The predominance of Fe3+ in zinkgruvanite and cerchiaraite contrasts with the stratiform Zn-Pb-Ag
mineralization in general, which although being Fe-enriched
is virtually devoid of Fe3+ . The great depth of the discovery
location within the mineralization seem to preclude any influence of surficial oxidation, whereby alteration by oxidizedbrines is implicated.

https://doi.org/10.5194/ejm-33-659-2021

Author contributions. NJ found the mineral in a sample provided
by AZ and made preliminary chemical analyses. AZ produced thegraphical log core section. EJ, JL and AK made physical and opticalobservations. FC did the crystal structure solution and refinement.
DH and AK obtained and interpreted spectroscopic data. JM performed EPMA work. DH coordinated the manuscript preparation,with substantial contributions from FC, NJ and EJ.

Competing interests. The contact author has declared that neither
they nor their co-authors have any competing interests.

Disclaimer. Publisher’s note: Copernicus Publications remains
neutral with regard to jurisdictional claims in published maps andinstitutional affiliations.

Acknowledgements. The studied samples were collected during a
research project in which Nils Jansson and Anders Zetterqvist participated and which was carried out as part of the strategic national innovation programme for the Swedish mining and metalproducing industry (STRIM) of Vinnova, Formas and the Swedish
Energy Agency, with financial support from Zinkgruvan Mining
AB, the Boliden Group and Lovisagruvan AB. Zinkgruvan Mining is thanked for granting permission to publish the results. Torbjörn Lorin is thanked for the colour photograph of zinkgruvanite
in Fig. 2. Frank Hawthorne and Nikita V. Chukanov are thanked
for useful suggestions. Fernando Cámara acknowledges financial
support by the Ricerca Locale 2019 grant of the Università di Milano and from the Italian Ministry of Education, University andResearch (MIUR) through the project “Dipartimenti di Eccellenza
2018–2022”. Financial support for publication costs was generously
given by Zinkgruvan AB.

Eur. J. Mineral., 33, 659–673, 2021

672

F. Cámara et al.: Zinkgruvanite, a new ericssonite-group mineral

Financial support. This research has been supported by the Italian
Ministry of Education, University and Research (MIUR) and the
Università di Milano (Dipartimenti di Eccellenza 2018–2022 andRicerca Locale 2019).

Review statement. This paper was edited by Cristian Biagioni andreviewed by Frank Hawthorne and Nikita V. Chukanov.

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