The Lengenbach Quarry in Switzerland: Classic Locality for Rare Thallium Sulfosalts

Abstract

The Lengenbach quarry is a world-famous mineral locality, especially known for its rare and well-crystallized Tl, Pb, Ag, and Cu bearing sulfosalts. As of June 2018, it is the type locality for 44 different mineral species, making it one of the most prolific localities worldwide. A total of 33 thallium mineral species have been identified, 23 of which are type minerals. A brief description of several thallium species of special interest follows a concise and general overview of the thallium mineralization.

Full text

Minerals 2018, 8, 409; doi:10.3390/min8090409 www.mdpi.com/journal/minerals
Review
The Lengenbach Quarry in Switzerland: Classic
Locality for Rare Thallium Sulfosalts †
Thomas Raber 1,* and Philippe Roth 1,2
1 Lengenbach Research Association (Forschungsgemeinschaft Lengenbach, FGL), Gemeinde Binn,
Dorfstr. 11, 3996 Binn, Switzerland
2 Swiss Seismological Service, ETH Zurich, Sonneggstr. 5, 8092 Zurich, Switzerland; phroth@sunrise.ch
* Correspondence: thomas.raber@kabelbw.de
† Anniversary publication—60 years of continuous mineral search at Lengenbach and 15 years of FGL.
Received: 11 July 2018; Accepted: 6 September 2018; Published: 14 September 2018
Abstract: The Lengenbach quarry is a world-famous mineral locality, especially known for its rare
and well-crystallized Tl, Pb, Ag, and Cu bearing sulfosalts. As of June 2018, it is the type locality for
44 different mineral species, making it one of the most prolific localities worldwide. A total of 33
thallium mineral species have been identified, 23 of which are type minerals. A brief description of
several thallium species of special interest follows a concise and general overview of the thallium
mineralization.
Keywords: Lengenbach; Binn valley; thallium; sulfosalts; hutchinsonite; fangite; richardsollyite;
sartorite; routhierite-stalderite; chabournéite-dalnegroite
1. Introduction
The Lengenbach quarry in the Binn valley, Valais, Switzerland (Figures 1 and 2) is located in
Triassic meta-dolomites of the Penninic zone in the Swiss Alps. Metal extraction for economic
purposes never occurred in the quarry, but specimen extraction has been continuously carried out
since 1958. The quarry is currently operated by the Forschungsgemeinschaft Lengenbach (FGL,
literally: Lengenbach Research Association), financed by a group of idealistic collectors and by the
local community of Binn. The purpose of the research association is to promote scientific research on
the unique minerals of the Lengenbach deposit and of other dolomite localities in the Binn valley. An
intermittent, measured specimen extraction during the snow-free summer months shall guarantee
the potential for scientific investigations on the one hand and deliver dolomite material for a
publicly accessible dump, serving as an attraction to equally eager tourists and mineral collectors, on
the other hand.
This brief review gives a glimpse at the current status of the mineralogical research with regard
to the thallium mineralization at the locality. For further information about history, geology, and
mineral extracting work we recommend References [1,2].

Minerals 2018, 8, 409 2 of 16
Figure 1. The upper part of the Lengenbach quarry in the Binn valley, view to the east.
Figure 2. Ralph Cannon, technical head of the Forschungsgemeinschaft Lengenbach (FGL) research
association, at the entrance of the quarry in front of the concrete hall, where the current
mineral-extraction activities are carried out at the lowest dolomite level.
2. Geochemical Setting and Formation of the Lengenbach Locality
The Lengenbach ore body is located within the Penninic Monte Leone nappe, at the Northern
front and subvertical hinge zone of a large fold. The stratabound mineralization occurs in the
stratigraphically uppermost part of the 240 m thick dolomite sequence.
The formation of the highly complex mineralization in the Lengenbach deposit is not yet
completely understood. While Graeser [3] suggested a late introduction of As, Tl, and Cu into a
pre-existing Fe-Pb-Zn mineralization during Alpine metamorphism from the underlying gneissic
basement, Hofmann and Knill [4] proposed a pre-Alpine origin of those elements and a subsequent
isochemical Alpine metamorphism, under upper greenschist to lower amphibolite facies.

Minerals 2018, 8, 409 3 of 16
According to Hofmann and Knill [4], the distinct mineral associations in the different parts of
the Lengenbach dolomite can be understood as a result of slow crystallization processes in two
different redox environments. One is based on graphite and/or pyrite–pyrrhotite, leading to
zerovalent arsenic. The other, which was essential for the rare sulfosalts’ formation, is controlled by
baryte (sulfate)–pyrite (sulfide), leading to trivalent arsenic. Accordingly, the As(III)-rich zone in the
central part of the quarry shows an enrichment in baryte and hosts the coveted Tl-Pb-Ag-Cu bearing
sulfosalts.
Graeser [3] as well as Hofmann and Knill [4] have each proposed a zonation scheme for the
different types of mineral assemblages. While the former considers in essence only mineralogical
and spatial criteria, the later rely on geochemistry and there is no obvious link between the two
zonations. However, it is clear that the Tl-rich zone is restricted to the central part of the quarry.
While on a broad scale the different bedding-parallel zones containing the different assemblages
strike subvertically in an east–west direction (Figure 1), on the more local scale, they can be
subdivided into ribbons and ellipsoidal lenses that thicken, to a maximum thickness of 0.5 m, and
pinch out.
The FGL has been working for a few years on three such ribbons in the Tl-rich central zone
(Figure 3). They are spaced approximately 1 m apart, measure a maximum of 4 m × 2 m and are
designated, from north to south as ribbons 1, 1/2, and 2. Structurally, they are ellipsoidal in shape,
with a sharp contact to the surrounding, mineral-poor dolomite. The contrast is essentially a
mineralogical-geochemical, not a lithological contrast. Thanks to their high realgar contents, all three
ribbons are easily identified in situ. But while ribbon 1 is very rich in thallium species, the very
brittle and orpiment-rich dolomite of ribbon 1/2 is poorer in Tl while the realgar-richest ribbon 2 is
almost bare of any thallium-species. Table 1 summarizes all species found in ribbon 1; 18 species
containing thallium as one of main constituents are marked in bold characters.
Figure 3. Three realgar-rich ribbons in the central dolomite zone in the lower part of the quarry.
Ribbon 1 (red) is very rich in thallium species, ribbon 1/2 (yellow) contains much orpiment in a brittle
dolomite and is poorer in thallium, ribbon 2 (orange) is the realgar-richest ribbon, but almost bare of
any thallium species. The maximum ribbon thickness is about 0.5 m. Dashed lines show the expected
extension of the ribbons below the debris.

Minerals 2018, 8, 409 4 of 16
Table 1. Species constituting the mineral assemblage of ribbon 1 in the Lengenbach quarry. Tl
minerals are marked in bold, modified after reference [5].
“Adularia” and “hyalophane”
Hutchinsonite
Rathite
Aktashite
Hydrocerussite
Realgar
Argentobaumhauerite
Incomsartorite
Richardsollyite
Argentodufrénoysite
Imhofite
Routhierite
Argentoliveingite
Jentschite
Rutile
Arsenic
Jordanite
Sartorite
Baryte
Kaolinite
Seligmannite
Baumhauerite
Lengenbachite
Silver
Bernardite
Liveingite
Sinnerite
Canfieldite (Te-rich)
Marrite
Smithite
Cerussite
Muscovite
Sphalerite
Coffinite
Nowackiite
Stalderite
Covellite
Orpiment
Tennantite
Dolomite
Pararealgar
Thalcusite
Dravite
Parapierrotite
Thorite
Dufrénoysite
Picotpaulite
Tochilinite
Edenharterite
Proustite
Trechmannite
Erniggliite
Pyrite
Uraninite
Ferrostalderite
Quadratite
Wallisite
Galena
Quartz
Wurtzite
Hatchite
Ralphcannonite
Xanthoconite
3. Overview of Thallium Minerals at Lengenbach
As of June 2018, the Lengenbach quarry hosts 160 different mineral species, with sulfides and
sulfosalts being the major group representing 57% of these species (Table 2 and Figure 4). Forty-four
minerals are so called type minerals as they have been found and described for the first time from
this locality. Twenty-three of them are thallium minerals. Table 3 lists all known Lengenbach
thallium minerals as of today.
Table 2. Mineralogical overview of the Lengenbach quarry.
Category
Number
Mineral species *
160
Elements
6
Sulfides and sulfosalts
91
Chalcogenides
2
Carbonates
10
Sulfates and molybdates
10
Phosphates and arsenates
8
Oxides
13
Silicates
20
Type minerals
44
Thallium minerals
33
* IMA (International Mineralogical Association) approved.

Minerals 2018, 8, 409 5 of 16
Figure 4. Distribution of mineral classes at Lengenbach.
Table 3. Thallium minerals at Lengenbach.
Mineral Species
Chemical Formula
Year of First Description
from Lengenbach
Reference for the Occurrence
at Lengenbach
Bernardite
Tl(As,Sb)5S8
1992
Graeser (in Hofmann et al.) [6]
Chabournéite
Tl4Pb2(Sb,As)20S34
2017
Roth [7]
Dalnegroite *
Tl4Pb2(As,Sb)20S34
2009
Nestola et al. [8]
Dekatriasartorite *
TlPb58As97S204
2017
Topa et al. [9]
Edenharterite *
TlPbAs3S6
1992
Graeser & Schwander [10]
Enneasartorite *
Tl6Pb32As70S140
2017
Topa et al. [11]
Erniggliite *
Tl2SnAs2S6
1992
Graeser et al. [12]
Fangite
Tl3AsS4
2017
Roth [13]
Ferrostalderite *
CuFe2TlAs2S6
2016
Biagioni et al. [14]
Gabrielite *
Tl2AgCu2As3S7
2006
Graeser et al. [15]
Hatchite *
AgTlPbAs2S5
1912
Solly & Smith [16]
Hendekasartorite *
Tl2Pb48As82S172
2017
Topa et al. [11]
Heptasartorite *
Tl7Pb22As55S108
2017
Topa et al. [11]
Hutchinsonite *
TlPbAs5S9
1905
Solly [17]
Imhofite *
Tl5.6As15S25.3
1965
Burri et al. [18]
Incomsartorite *
Tl6Pb144As246S516
2016
Topa et al. [19]
Jentschite *
TlPbAs2SbS6
1997
Graeser & Edenharter [20]
Lorándite
TlAsS2
1967
Graeser [21]
Parapierrotite
Tl(Sb,As)5S8
2016
Raber [22]
Philrothite *
TlAs3S5
2014
Bindi et al. [23]
Picotpaulite
TlFe2S3
2015
Roth [24]
Raberite *
Tl5Ag4As6SbS15
2012
Bindi et al. [25]
Raguinite
TlFeS2
2017
Roth [26]
Ralphcannonite *
AgZn2TlAs2S6
2015
Bindi et al. [27]
Rathite *
Ag2Pb12-xTlx/2As18+x/2S40
1896
Baumhauer [28]
Richardsollyite *
TlPbAsS3
2017
Meisser et al. [5]
Routhierite
CuHg2TlAs2S6
2016
Roth [29]
Sicherite *
TlAg2(As,Sb)3S6
2001
Graeser et al. [30]
Spaltiite *
Tl2Cu2As2S5
2014
Graeser et al. [31]
Stalderite *
CuZn2TlAs2S6
1995
Graeser et al. [32]
Thalcusite
Tl2Cu3FeS4
2005
Cannon [33]
Wallisite *
CuTlPbAs2S5
1965
Nowacki [34]
Weissbergite
TlSbS2
2014
Raber & Roth [35]
* Type minerals from the Lengenbach quarry.
From the 73 valid mineral species containing essential thallium worldwide (according to
mindat.org [36]), the striking number of 33 species (45.2%) could be found at Lengenbach.
Elements
4%
Sulfides &
sulfosalts
57%
Chalcogenids
1%
Carbonates
6%
Sulfates & molybdates
6%
Phosphates &
arsenates
5%
Oxides
8%
Silicates
13%

Minerals 2018, 8, 409 6 of 16
4. On Some Special Thallium Minerals from the Lengenbach Quarry
We focus here on a few thallium species of special interest, as a discussion of all thallium
sulfosalts would be beyond the scope of this brief note.
4.1. Hutchinsonite—The First of Its Kind
The first thallium mineral from Lengenbach, hutchinsonite, TlPbAs5S9, was found in 1903, when
the English expert of Lengenbach minerals, Richard Harrison Solly (1851–1925), during one of his
many trips to this remote Binn valley, recognized that the red to greyish-black, often flattened
orthorhombic crystals probably were belonging to a new species. He briefly described it in 1904 [37],
without giving it a name. In 1905, his colleague at the British Museum, G.T. Prior was able to reveal
the presence of 20 wt % Tl in hutchinsonite. This was of “especial interest”, as Solly [17] wrote in his
following detailed description, in which he named the mineral after Arthur Hutchinson (1866–1937).
Prior’s discovery of thallium in hutchinsonite was important enough to result in a short note in
Nature [38], as it was only the third mineral worldwide (after crookesite and lorándite) to contain
thallium as an essential constituent.
Hutchinsonite is the most common thallium species in the deposit and represents the type
structure of a family of complex sulfosalts. Its crystals are commonly transparent and prismatic, due
to an elongation parallel to the c axis (see Figures 5–7), or, rarely, more or less isometric.
Hutchinsonite may contain antimony that contributes the crystals to be darker and opaque. The two
varieties, prismatic Sb-free and more isometric Sb-bearing hutchinsonites, may be closely associated.
The crystals reach 2 mm in size.
Figure 5. Dark wine-red, transparent, lath-like hutchinsonite crystals on dolomite. Field of view 1.4
mm. Photo: Edgar Müller.

Minerals 2018, 8, 409 7 of 16
Figure 6. Translucent aggregate of parallel-oriented, red, flattened hutchinsonite crystals with pyrite
on dolomite. Field of view: 2.5 mm. Photo: Stephan Wolfsried.
Figure 7. Prismatic dark-red to grey crystals of hutchinsonite. Field of view: 1.5 mm. Photo: Stephan
Wolfsried.
4.2. Fangite—The Thallium-Richest
Well-developed crystals of fangite, Tl3AsS4, could recently be identified for the first time
[13]—to our knowledge, the first microscopically visible crystals of this species worldwide. They are
small, deep red, and very shiny (Figure 8). With more than 75 wt % Tl, fangite is the thallium-richest
mineral discovered at Lengenbach up to now.
A morphological study of the small crystals [26] showed them to display different combinations
of crystal forms, irrespective of the fact that the prismatic habit is always approximately the same
(Figure 9).

Minerals 2018, 8, 409 8 of 16
Figure 8. Tiny, prismatic, lustrous, red fangite crystals on dolomite. Field of view: 0.75 mm. Photo:
Mischa Crumbach.
Figure 9. Fangite crystals showing different combinations of forms but similar habits. A distinct
color is assigned to each crystal form. The Miller indices of the different forms are given without
brackets FACES drawings [39].
4.3. Richardsollyite—Honoring a Pioneer
In 2015, the FGL extracted two specimens with an unknown mineral from the very Tl-rich
dolomite ribbon 1 (Figure 3) in the center of the quarry. Its chemistry, as first determined by Energy
Dispersive X-ray Spectroscopy (EDXS) measurements in two independent institutes, showed the
presence of Tl, Pb, As, and S in a simple, yet unknown ratio of 1:1:1:3. Also the powder X-ray
diagram did not match with any known listed natural or synthetic chemical compound in the
relevant databases. One year later, Meisser et al. [5] could describe this mineral as a new species with
the name richardsollyite (Figure 10), TlPbAsS3, honoring the aforementioned pioneer of Lengenbach
investigations at the dawn of the twentieth century, R.H. Solly. The crystal structure of
richardsollyite is new in nature, being previously known only in some synthetic alkali sulfosalts [5].

Minerals 2018, 8, 409 9 of 16
Figure 10. Holotype specimen of richardsollyite (dark grey) with hutchinsonite (dark red) and
realgar. Field of view: 3.5 mm. Mineralogical Collection of the Musée cantonal de géologie (MGL no.
080126), photo: Stefan Ansermet.
4.4. The New “Sartorites”—From a Species to a Group
Sartorite, PbAs2S4, was first described by vom Rath as “scleroclase” in 1864 [40], and shortly
after renamed by Dana [41] to honor Wolfgang Sartorius von Waltershausen (1809–1876), a professor
of mineralogy in Göttingen, Germany. In 1919, Smith and Solly [42] recognized that sartorite
has—despite its simple chemical formula—a quite unique and complex crystal structure: “sartorite
appears to rank with the telluride of gold, calaverite, in the peculiarity of its atomic arrangement, since in
certain at least of his crystals there exist simultaneously two or even three incongruent space-lattices, which
may be supposed derivable from one another by a slight shear.” It is quite remarkable that they were able,
with the limited methods of their time—in essence only crystal-morphological investigations—to
recognize the so-called complex and incommensurate nature of both the calaverite and, partly,
sartorite structures.
After the introduction of X-ray investigations in crystallography, several different monoclinic
super cells (superstructures) were described [43–46]. Berlepsch et al. [46] pointed to the
crystallographic consequences of the complex correlated atomic substitution by which substantial
amounts of thallium are incorporated into the sartorite structure. They found a so-called 9-fold
superstructure for a sartorite with up to 6.5 wt % Tl and discussed this as a “lock-in” structure with a
commensurate lattice, for a species that they regarded as usually incommensurate.
The true nature of sartorite was finally resolved by Topa et al. [9,11,19]. Based on a systematic
combination of electron microprobe measurements and crystal structure determinations they
showed that “sartorite” actually represents a group of different mineral species with distinct crystal
structures and distinct chemical compositions. According to their different superstructures, the new
“sartorites” were named by adding a Greek prefix, which corresponds to an integral multiple of the
basic “sartorite” substructure with 4.2 Å (Table 4).

Minerals 2018, 8, 409 10 of 16
Table 4. The new sartorite minerals.
Mineral Name
Chemical Formula
Superstructure of the Sartorite Subcell (4.2 Å)
Heptasartorite [11]
Tl7Pb22As55S108
7-fold
Enneasartorite [11]
Tl6Pb32As70S140
9-fold
Hendekasartorite [11]
Tl2Pb48As82S172
11-fold
Incomsartorite [19]
Tl6Pb144As246S516
11-fold (incommensurate)
Dekatriasartorite [9]
TlPb58As97S204
13-fold
These species are not visually distinguishable. The crystals are lead-grey with a metallic luster.
Well-developed crystals show a prismatic habit with more or less distinct striation parallel to the
longitudinal axis (Figure 11). Their length reaches several centimeters.
Figure 11. Lead-grey, metallic, prismatic crystal of dekatriasartorite. Field of view 4.8 mm. Photo:
Mischa Crumbach.
4.5. The Routhierite-Stalderite Group—Complex Substitutions
The routhierite-stalderite series is a group of thallium arsenio-sulfosalts with, in addition,
monovalent (Me1: Cu+, Ag+) and bivalent metal ions (Me2: Hg2+, Zn2+, Fe2+) and the generic formula
TlMe1+Me22+As2S6. Accordingly, six different combinations, and thus six distinct mineral species are
theoretically possible in this group (Table 5, Figure 12). Five could indeed be found in nature:
arsiccioite, routhierite, stalderite, ralphcannonite, and ferrostalderite. The latter four occur in the
Lengenbach quarry, the type-locality for the latter three. Routhierite and arsiccioite are red to
dark-red in color, the other three are dark grey with a metallic luster, but they all show the same
pseudo-cubic to prismatic morphology (≤1 mm).

Minerals 2018, 8, 409 11 of 16
Table 5. Routhierite-stalderite group minerals.
Mineral Species
Chemical Formula
Routhierite
TlCuHg2As2S6
Stalderite
TlCuZn2As2S6
Ferrostalderite
TlCuFe2As2S6
Ralphcannonite
TlAgZn2As2S6
Arsiccioite
TlAgHg2As2S6
Unknown
TlAgFe2As2S6
Figure 12. The minerals of the routhierite-stalderite group in a block diagram. The six distinct
species are the result of the six possible combinations of monovalent (Ag+, Cu+) and bivalent metal
ions (Zn2+, Hg2+, Fe2+). Modified after Reference [27].
In the frame of a series of EDXS analyses on Lengenbach samples from the mineralogical
collection of the Eidgenössiche Technische Hochschule (ETH) collection in Zurich, we recently
identified what to our knowledge are the first completely idiomorphic crystals of routhierite
worldwide (Figure 13).
Arsiccioite has not yet been found at Lengenbach. However, a single EDXS analysis of a minute
crystal indicated a possible dominance of silver and iron, and thus, the possible existence of the last
unreported member of this group in the quarry.

Minerals 2018, 8, 409 12 of 16
Figure 13. Idiomorphic, pseudo-cubic crystals of routhierite from the mineralogical collection of the
Eidgenössiche Technische Hochschule ETH in Zurich.
4.6. Chabournéite-Dalnegroite—And Possibly More
Dalnegroite was described as a new mineral species from Lengenbach in 2009 [8]. It is
considered the As-analogue of chabournéite. The latter was also recently identified in one single
specimen showing what appears to be the first distinct crystals for the species: They are very similar
to the dalnegroite crystals and also show a strong similarity to lengenbachite crystals, which may
imply that the two rare species may have been mistaken for lengenbachite in the past (Figure 14).
Both dalnegroite and chabournéite are Pb-bearing species. In ribbon 1/2, however, the FGL has
recently found a few samples of a Pb-free dalnegroite (Figure 15), the equivalent of the Pb-free
chabournéite from Jas Roux, France [47,48]. The Pb-free species may well be distinct minerals
(Figure 16). Their study needs to be refined and completed.
Figure 14. Black, stellar aggregates of chabournéite on dolomite. Field of view 1.2 mm. Photo: M.
Crumbach.

Minerals 2018, 8, 409 13 of 16
Figure 15. Aggregate of small acicular crystals of “Pb-free dalnegroite” from ribbon 1. Field of view
0.6 mm.
Figure 16. Diagram of Jas Roux and Abuta (France, resp. Japan, open diamonds)
chabournéite,Monte Arsiccio (Italy, open circles) protochabournéite and Lengenbach (open squares)
dalnegroite, modified after Reference [48], with copyright permission from Mineralogical
Association of Canada, 2013. Dalnegroites are located in the As-dominated left part of the diagram,
chabournéites and protochabournéites in the right part with Sb-dominance. The Pb content
increases along the y-axis. The new Lengenbach samples (analyzed by EDXS) are shown as red
squares. Lengenbach chabournéite is located in the Pb-rich part of the diagram (the cross gives the 
1 sigma of all measurements), showing a higher Sb content than the samples from Jas Roux. The
nearly Pb-free dalnegroite seems to be clearly isolated from the holotype material of this species
(open squares).

Minerals 2018, 8, 409 14 of 16
5. Summary and Perspective
Since 1958 an uninterrupted prospection for and extraction of mineral specimens has been
performed in the Lengenbach quarry. Three working collectives have been successively in charge of
these purely non-profit operations, aimed at providing interesting specimens to both science and
collector communities. The Arbeitsgemeinschaft Lengenbach (AGL, literally: Lengenbach Working
Association) was active from 1958 to 1997 and extracted 28,422 specimens in total. It was followed by
the Interessengemeinschaft Lengenbach (IGL, literally: Lengenbach Interest Association), active from
1998 to 2002. The IGL produced 2424 specimens. The Forschungsgemeinschaft Lengenbach (FGL),
which was founded in 2003 and celebrates its 15th anniversary in 2018, has been extremely
successful. The association could ensure the collaboration of several experts as Preferred Associated
Scientists, who performed countless investigations to increase our knowledge of the Lengenbach
mineralogy, and to contribute with many publications and the description of several new mineral
species to further enhance Lengenbach’s reputation as an eldorado for rare and complex sulfosalts.
In these 15 years, 43 new mineral species have been described from the Lengenbach quarry,
including 17 new type minerals.
As a consequence of the specimen extraction performed since 2014 in the Tl-rich dolomite
ribbon 1, the number of thallium-bearing mineral samples extracted in the quarry has significantly
increased recently, as it was already the case in the late eighties and early nineties when the AGL
also worked in this zone (Figure 17). The FGL plans to continue the mineral prospection and
extraction during the next two or three years in this fascinating part of the deposit. Consequently,
there is a good chance to find additional rare thallium sulfosalts and—who knows—eventually also
new mineral species.
Figure 17. Number of thallium bearing samples officially cataloged by the three working
associations, since 1958.
Author Contributions: Both authors (T.R. and P.R.) contributed to varying degrees to all the different aspects
of the work that led to this article. This includes conception, investigations, formal analyses, validation, draft
preparation, review and editing, as well as administration.
Funding: This research received no external funding.
Acknowledgments: We would like to thank the “Verein Freunde Lengenbach” association, for its yearly financial
contribution, and their members for their active support to the operational work in the quarry during their
summer holidays. Special thanks go to FGL’s Scientific Head, Nicolas Meisser (Lausanne, Switzerland) and to
our Preferred Associated Scientists who are always willing to investigate interesting mineral samples from the
quarry, and without whom the incredible mineralogical success of the Lengenbach as worldwide-renowned
sulfosalt locality would not have been possible: Fabrizio Nestola (Padua, Italy), Jakub Plášil (Prague, Czech
Republic), Dan Topa (Vienna, Austria). Thanks also go to three anonymous reviewers who substantially
helped improve this work. We are also grateful to the Minerals editors for their thorough and thoughtful
editing.
0
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100
150
200
250
300
350
400
Number
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Minerals 2018, 8, 409 15 of 16
Conflicts of Interest: The authors declare no conflict of interest.
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