Welcome on the new web site of the Forschungsgemeinschaft Lengenbach (FGL). This is the official website of the Lengenbach Research Association.
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)
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-solution.The next issue will contain a note on debattistiite. The series is expected to go on on a more or less regular basis.
February, 2016 - The Mineralogical Magazine is about to release a paper by PAS Dan Topa and Emil Makovicky on the renamed mineral argentobaumhauerite (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, uraniferous 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 worldwide, 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."Ralphcannonite crystals (photo T. Raber, courtesy PIAG)
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 platty 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.
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.