Welcome to the official web site of the Lengenbach Research Association, FGL, Forschungsgemeinschaft Lengenbach.
Geocronite from Lengenbach?
Dekatriasartorite, the 5th 'M-sartorite'
December 21, 2017 – Dan Topa, one of the FGL Preferred Associated Scientists (PAS), has just seen his fifth member of the sartorite series been officially and publicly approved by the CNMNC. Knowing the naming scheme of the previous new ‘sartorites’ (see the Feb. 2016 contribution below), it is easy to infer that the new species, dekatriasartorite, received its name from its 13-fold superstructure. Its (simplified) formula is TlPb58As97S204. This is the Tl-poorest of the new ‘satorites’, also called M-sartorites (see the now published article on three such new M-sartorites; Topa et al., 2017). As it is the case for most of the prismatic, grey Lengenbach Pb sulfosalts, a reliable identification is only possible with thorough analytical investigations. Interestingly, and in contrast to other members of the sartorite homologous series such as baumhauerite or rathite, most of the investigated samples of M-sartorites are homogeneous. As a product of a late sulfide deposition phase, the M-sartorites tend to cover or replace all other earlier formed Pb-sulfosalts (Topa et al., 2017).
Report on the 2nd International Sulfosalt Symposium in Tavagnasco (08/2017)
New Lengenbach Brochure
June, 2017 - There is a brand new Lengenbach brochure (in German language only, edited by the Natural Park Binntal) with many facts and information for collectors and tourists, including gorgeous mineral photos. Have a look!
Raguinite, yet Another Premiere
March, 2017 - Nicolas Meisser, using a combination of XRD and EDXS methods, just reported raguinite as a new Lengenbach mineral. The specimen (L-15-6772, LB_UK-097) hosting it was extracted in 2015 from the Tl-rich dolomite ribbon on which the FGL has been working for three years now. Raguinite builds a black crust on a wallisite crystal (wallisite62hatchite38). Under strong magnification raguinite shows tiny aggregates of platy, rectangular crystals.
Coffinite Crystal Structure Solved
January 6, 2017 - PAS (Preferred Associated Scientist) Jakub Plášil just announced that he was able to solve for the first time the crystal structure of natural coffinite from single-crystal data. The data was acquired on a coffinite sample mined in 2015 in the Lengenbach quarry, the counterpart of the specimen pictured below, It was speculated - when very recently (s. below) coffinite was identified for the first time in the quarry - that Lengenbach coffinite might diffract, as brannerite had shown in the past not to be metamict. This turned out to be true. More to come in a future paper.
Richardsollyite, a new Mineral and a new Structure
October 5, 2016 - Early in the season 2015, the FGL extracted a specimen with an unknown mineral from the Tl-rich dolomite ribbon, called "B1", in the center of the quarry. One year later, we can announce the approval of richardsollyite as a new mineral. Richardsollyite occurs as metallic, grey-black crystals with striated and curved faces, grown on cherry-red hutchinsonite (see picture). The structure of richardsollyite, TlPbAsS3, is new, without natural equivalent. The name honours Richard Harrison Solly (1851-1925), eminent British mineralogist, very present and successful in the Binn valley at the dawn of the at the dawn of the twentieth century.
First Occurrence of Schultenite
September 21, 2016 - Based on powder XRD analyses, Nicolas Meisser, scientific head of the FGL, just confirmed what had first been supposed based on a routine EDXS measurement: schultenite has to be added to the list of Lengenbach mineral. This is the first reported occurrence in Switzerland. On a specimen mined by the FGL in summer 2016 from „ribbon 2“, in the central, As-rich part of the mineralization, two secondary minerals occur on native arsenic: arsenolite octahedra and schultenite as apparently porous, platy, beige crystals that, under the SEM, appear to consist of numerous tiny triangles and platelets.
Three New "Sartorites"
February 9, 2016 - The approval by the CNMNC of three new sulfosalts from Lengenbach has just been announced. Congratulations to the main author, Dan Topa, with whom the FGL has recently signed a Preferred Associated Scientist (PAS) collaboration. The three new minerals heptasartorite, enneasartorite and hendekasartorite are all - as their name says - members of a "subgroup' of the sartorite homologous series. In the course of systematic investigations Dan has observed a systematic correlation between the amount of Tl in "sartorite" and the crystal structure. At a few critical values of Tl content the crystal structure tilts into a new one, leading to a new species. "Sartorite" is now the designation for a group of minerals (no holotype is known for this species on which investigations could have been performed). As it is the case for most of the prismatic, grey Lengenbach Pb sulfosalts a distinction between the new minerals is only possible with thorough analytical investigations.
Ferrostalderite, the 35th Type Mineral
May 4, 2015 - The CNMNC just announced the approval of ferrostalderite, a new mineral from Lengenbach. This is yet another member of the routhierite-stalderite isotopic series, to which ralphcannonite has just recently been added. Ferrostalderite has the ideal formula: CuFe2TlAs2S6. It cannot be distinguisehd visually from stalderite and ralphcannonite, all three mineral species forming small, equant to prismatic, tetragonal crystals. March 17, 2016. The characterizazion paper is now published (see here).
Two Additional Secondary Minerals
September 12, 2015. Nicolas Meisser, scientific head of the FGL, announces the identification on samples from the Musée cantonal de Géologie in Lausanne (CH) of two new secondary minerals: leadhillite and bianchite.Leadhillite was found as up to 0.04 mm greasy white, hexagonal crystals on altered lengenbachite associated with mimetite on a specimen mined in 1979. Bianchite occurs as to 0.2 mm large, snowy white efflorescences on pyrite and is intimately associated with sphalerite on a specimen from 1980.
3rd Locality for Picotpaulite
June 19, 2015 - An XRD analysis performed today at the Padova Univ. by PAS Prof. Fabrizio Nestola just confirmed the existence of picotpaulite at Lengenbach, after first EDX analyses conducted on a FGL specimen found in 2014 had already indicated the possible presence of this rare iron-thallium sulfide (TlFe2S3) for which the quarry is now the third locality worldwide. Picotpaulite forms a crust of dull grey, tiny crystals on a larger pyrite crystal in the Tl-rich band 1 of zone 1 of the quarry, a zone carefully exploited in 2014.
© Mischa Crumbach / designbyearth.com, FOV 0.35 mm.
Spaltiite, the 32nd Type Mineral
June 30, 2014 - The Commission on New Minerals, Nomenclature and Classification (CNMNC) of the International Mineralogical Association (IMA) just announced the approval of spaltiite, a new mineral from Lengenbach. It has the formula: Tl2Cu2As2S5. The mineral, submitted by Graeser et al., owes its name to its extreme propensity to cleave (German: spalten). It is reported to form up to 2 mm long, prismatic crystals. A second specimen was recently identified in Milan (see SEM image). More will be written here, when the full caracterization of the new species is published.
Large Article in Mineralogical Record
March 2014. Since 1977 nothing had been published in the Mineralogical Record on the Lengenbach quarry. The extensive article published in Spring 2014 (Vol. 45, no. 2) filled that gap. This is the most recent and complete compilation, with descriptions of all rare minerals known to occur in the quarry as of Dec. 2013. The paper is illustrated with many new and excellent photographs by Matthias Reinhardt, Mischa Crumbach and Stefan Wolfsried. It is dedicated to Stefan Graeser.
Metanovácekite, an U Arsenate at Lb
March 5, 2014. FGL member Dr. Nicolas Meisser announces the identification of metnovácekite at Lengenbach (coll. T. Raber). XRD and EDS analyses have shown a mineral earlier reported as possible chadwickite (Graeser et al. 2008: Faszination Lengenbach) to be the Mg-U arsenate metanovácekite. The mineral contains small amounts of Cu, it is P-free. SEM images show that the smooth light-green spherules oberved macroscopically actually consist of foliated rosettes.
Untwinned Sinnerite and Coloradoite
Oct. 26, 2013 - A specimen submitted by Luca De Battisti and investigated by Prof. Fabrizio Nestola turned out to be sinnerite, nothing exciting at Lengenbach apart from the fact that this was the first untwinned sinnerite ever x-rayed. This led to the refinement of the crystal structure of the species by Prof. Luca Bindi (Bindi et al. 2013). Since Hg had been observed surprisingly by L. De Battisti in the EDS measurements a WDS analysis was performed that revealed tiny inclusions of coloradoite (HgTe), the first mention of this mineral in the quarry.
Tiny granular sinnerite crystal on realgar (Photo Museo Civico di Storia Naturale, Milan)
Weissbergite, the First Sb Sulfosalt
July 26, 2013 - Prof. F. Nestola, the FGL 'Preferred Associated Scientist' has for the second time within six months positively identified weissbergite. The XRD data are nonambiguous. This represent the first Lb sulfosalt with dominant Sb. The EDX measurement at PIAG had shown the Sb:As ratio to be approx. 2.0, qualifying the mineral as As-rich weissbergite. The columnar grey crystals were found in the As-rich zone in 1989 & 1990.
First Mention of Diaphorite
February 15, 2018 - On a specimen extracted from the quarry in 1996 (LB_UK-131), Prof. Fabrizio Nestola (Padua, I) identified diaphorite, the first mention of this sulfosalt at Lengenbach. The specimen shows twinned prismatic crystals (up to 0.4 mm) associated with sphalerite and galena. They show a superficial alteration that made the EDXS measurements of little use. A WDS analysis made on a polished section of one crystal now gave the formula Pb1.93Ag3.12Sb3.11As0.13S8 (calculated for 8 S atoms). A second phase, still under investigation, is accessorily associated in the crystals, with the same elements but with different ratios. According to analogies described in literature, the twin plane in these crystals is most probably (120).
Three New Sulfates
January 22, 2018 – Nicolas Meisser (Lausanne), scientific head of the FGL, identified three new sulfates as neoformations on oxidized pyrite samples by combined XRD and EDXS analytical methods: ferrohexahydrite, FeSO4 · 6H2O, rozenite, FeSO4 · 4H2O, and starkeyite, MgSO4 · 4H2O. Ferrohexahydrite forms yellowish, earthy crusts associated with hexahydrite. Rozenite and starkeyite show colorless, capillary efflorescences, the latter only as admixture with the former.
Routhierite - the First Crystals
January 27, 2018 - Routhierite had been suspected from Lengenbach for a while, but its formal identification by F. Nestola, did not took place before 2016. The mineral forms xenomorph inclusions in realgar. In the frame of a series of EDXS analyses on samples from the ETH collection in Zurich, we now found the first crystals. This is significant inasmuch as to our knowledge these are also the first crystals worldwide. Not surprisingly, they show the same morphology as the other Lengenbach members of the group (stalderite, ralphcannonite and ferrostalderite): pseudo-cubic tetragonal prisms (≤0.1mm). Specimen L 26'896 that hosted them was extracted in 1996 and contains hutchinsonite and realgar. Chemically, the crystals show a pronounced Hg and Cu dominance (over Zn, Fe, as well as Ag, respectively).
Aktashite, New for Lengenbach
February, 2017 - In the Tl-rich dolomite ribbon on which the FGL has been working for three years now, very late stage, spongy grains frequently occupy semi-spherical cavities in realgar. These grains have shown to be sinnerite but recently aktashite has also been identified (EDXS in Zurich and XRD in Lausanne) for the first time in the quarry (and in Switzerland). Chemically aktashite can be seen as sinnerite + Hg3S3. Further work is needed to test the homogeneity of the grains (surficial mercurization or homogeneous grains?).
Fangite, the First Crystals
October 22, 2016 - Fangite was recently identified as a first occurrence from Lengenbach (EDXS P. Roth, 1st August 2016, XRD F. Nestola, 18th October 2016). The crystals, the first fangite crystals ever reported to our knowledge, are deep red, highly reflective, prismatic, small (up to 50 microns) and lie directly on dolomite or on orpiment. Their morphologies (there are two, both prismatic) could be convincingly modeled (see here). Both fangite specimens found so far were mined before 2000.
FOV 0.75mm. Copyright Mischa Crumbach / designbyearth.com
Argentodufrénoysite, Another Member of the Sartorite Homologous Series
November 11, 2016 - Another highlight in the sys- tematic work of Dan Topa on the Lengenbach members of the sartorite homologous series is the description of this new mineral: argentodufrénoysite. As in the pairs baum- hauerite-argentobaumhauerite and liviengite-argentoliveingite a Ag and As for 2Pb substitution controls the changes in the architecture of the structure and leads to this new member. One of the two cotype specimens was extracted by the FGL in 2011 on the highest and eastern-most excavation level of the quarry, in clefts locally filled with several sulphosalt phases. In both cotype specimens argentodufrénoysite forms ex- solution lamellae with Ag-bearing dufrénoysite.
Part of the 2011 cotype specimen. Copyright Mischa Crumbach / designbyearth.com. FOV 3.9 mm
Chabournéite, Sb-dominant Sulfosalt
October 22, 2016 - Recent investigations by P. Roth (EDXS, 1st November 2015) and F. Nestola (XRD, 18th October 2016) have proven the existence of cha- bournéite at Lengenbach. The mineral forms stellar aggregates of black, shiny acicular crystals associated to smithite. Their Pb content is similar to that of the original Jas-Roux material (x ~ 1). The Sb:As ratio is ~4 (see here for detailed data and SEM images). Even if Sb dominant minerals are rare at Lengenbach, chabournéite might be more common than suggested by the only specimen known, the strong macroscopic resemblance with lengenbachite having possibly contributed to misidentifications in the past..
Copyright Mischa Crumbach / designbyearth.com.
Incomsartorite, yet Another Sartorite
September 30, 2016 - Dan Topa has received notice of the approval of yet another sartorite mineral, the fourth one (see below): incomsartorite is the elevenfold incommensurate superstructure of sartorite homologues (with N=3). The simplified formula is Tl6Pb144As256S516. Incomsartorite was found during the systematic study of crystallized and massive members of the sartorite homologue series. Homogeneous, individual crystals (~0.3-0.5 mm) seem to be extremely rare.
Argentoliveingite, a New Species from an Old Sample
September, 2016 - Argentoliveingite was found by Topa et al. (2016) in a specimen acquired by the Natural History Museum Wien back in 1903. The new mineral, AgxPb40-2xAs48+xS112 (3<x<4), is closely associated with liveingite, baumhauerite and argentobaumhauerite but also forms rare, individual, chemically homogeneous crystals. Argentoliveingite is a new member of the sartorite homologous series with a N value of 3.67, like liveingite. The presence of silver controls the doubling of the c-axis, compared to the b-axis of liveingite, and the associated changes in the architecture of the structure. The mineral is almost certainly the insufficiently cha- racterized mineral "rathite-IV" (or "rathite-140") repea- tedly reported in the literature (see e.g. Graeser et al., 2008).
February, 2016 - The Mineralogical Magazine is about to release a paper by PAS Dan Topa and Emil Makovicky on the renamed mineral argento-baumhauerite (earlier called baumhauerite-2a) in which they clearly show that the mineral is an independent species and not a polytype as it had been speculated in the past (and is partly inferred from the old name). The authors describe the structure of argentobaumhauerite, with a remarkable unit-cell scale separation into alternating 'substituted' (Ag & As for Pb) and 'unsubstituted' N = 4 slabs (between the N = 3 slabs) and show the differences with the structure of baumhauerite. They also address the genesis of argentobaumhauerite that commonly forms two systems of exsolution lamellae at oblique angles in baumhauerite, see BSE image below.
First Occurrence of Coffinite
November, 2015. In the thallium-rich ribbon 1, urani- ferous minerals were found sporadically. Besides uraninite, found in a few distinct cubic crystals, Th-rich coffinite could also be identified based on EDXS measurements. As reported from other localities world- wide, Th and Ca partly replace here U, while P and As replace Si.
New Clay Species for Lengenbach
October 3, 2015. Nicolas Meisser, scientific head of the FGL, announces the identification on a sample from the Musée cantonal de Géologie in Lausanne (CH) mined in 2005 of a new clay mineral for the quarry: rectorite ("rectorite-K"). The composition is K10.5 Na0.5 Mg3.7 Ca1.4 Zn2.5 Si54.6 Al26.9 -O-F.
Yet Another Two New Minerals
March 26, 2015 - The CNMNC just announced the approval of another two new sulfosalts from Lengenbach. Congratulations to both FGL members Markus Ecker and Ralph Cannon for eckerite and ralphcannonite, respectively. The former is a Cu-Ag suflosalt, structurally related to xanthoconite, while the latter is another member of the routhierite isotypic series, the Ag-rich analogon of stalderite. Eckerite was found in 1995 and recognized by Graeser in 1998 to be a new mineral which received the working designation of 'kanisterite'. It is the first mineral of the group built by the solid solution series proustite-pyrargyrite and xanthoconite-pyrostilpnite to contain Cu as a main element. As Bindi et al. (2015) put it: "The exceptional conditions needed to form such a unique phase emphasize the geochemical distinctiveness of the Lengenbach deposit, able to produce rare minerals never discovered in other deposits."
Another New Sb Mineral for Lb
April 3, 2014. FGL member Luca De Battisti and PAS Prof. Fabrizio Nestola announce the identification of parapierrotite at Lengenbach (coll. LDB). First EDS analyses (LDB) had shown the mineral to be something like an Sb-rich imhofite. However, single crystal XRD investigations in Padua (FN) now clearly show the spherical aggregates of tiny platy crystals found in 1976 to be parapierrotite. In the past such dark brown aggregates of parapierrotite may well have been mis-identified as imhofite or lengenbachite.
Philrothite, Latest New Mineral from Lb
Feb. 6, 2014 - The first description of philrothite just appeared in the Mineralogical Magazine. Bindi et al. (2014) describe philrothite (IMA 2013-066), another new thallium sulfosalt from the Lengenbach quarry: TlAs3S5. It represents the N = 4 homologue of the sartorite homologous series. The new species was found as black xenomorph grains lying directly on realgar and associated with smithite, sartorite and rutile on a specimen most probably found in the old quarry. FGL member Luca De Battisti first recognized the tiny grains and performed promizing preliminary EDX analyses. The successful characterization followed in Florence (Prof. Bindi), Padova (Prof. Nestola) and Copenhagen (Prof, Mackovicky).
Dervillite, the Latest Lb Mineral
Sept. 19, 2013 - Prof. Luca Bindi with the help of Prof. Fabrizio Nestola just announced the identification of dervillite on a specimen submitted by Luca De Battisti. The single crystal was found in the jordanite paragenesis. The quality of the data acquired allowed the species to be redefined. A paper describing the redefinition and the crystal structure of dervillite has been published in the Mineralogical Magazine.The Lengenbach quarry is now the third location worldwide for this rare species.
New Lb Series in Schweizer Strahler
Aug. 2013 - The latest issue of Schweizer Strahler contains the first of a series of short articles to come on new discoveries made in the Lengenbach quarry. The first contribution by Dr. Thomas Raber is devoted to the minerals of the pearceite - polybasite solid-solu- tion.The next issue will contain a note on debattistiite. The series is expected to go on on a more or less regular basis.