Skip to main content Accessibility help

Dalnegroite, Tl5–x Pb2x (As,Sb)2l–x S34, a new thallium sulphosalt from Lengenbach quarry, Binntal, Switzerland

  • F. Nestola (a1), A. Guastoni (a1), L. Bindi (a2) and L. Secco (a1)


Dalnegroite, ideally Tl4Pb2(As12Sb8)Σ20S34, is a new mineral from Lengenbach, Binntal, Switzerland. It occurs as anhedral to subhedral grains up to 200 μm across, closely associated with realgar, pyrite, Sb-rich seligmanite in a gangue of dolomite. Dalnegroite is opaque with a submetallic lustre and shows a brownish-red streak. It is brittle; the Vickers hardness (VHN25) is 87 kg mm-2 (range: 69—101) (Mohs hardness ∼3—3½). In reflected light, dalnegroite is highly bireflectant and weakly pleochroic, from white to a slightly greenish-grey. In cross-polarized light, it is highly anisotropic with bluish to green rotation tints and red internal reflections.

According to chemical and X-ray diffraction data, dalnegroite appears to be isotypic with chabournéite, Tl5-x Pb2x (Sb,As)21-x S34. It is triclinic, probable space group P1, with a = 16.217(7) Å, b = 42.544(9) Å, c = 8.557(4) Å, α = 95.72(4)°, β = 90.25(4)°, γ = 96.78(4)°, V = 5832(4) Å3, Z = 4.

The nine strongest powder-diffraction lines [d(Å) (I/I 0) (hkl)] are: 3.927 (100) ( 10 0); 3.775 (45) (22); 3.685 (45) (60); 3.620 (50) (440); 3.124 (50) ( 2); 2.929 (60) (42); 2.850 (70) (42); 2.579 (45) (0 2); 2.097 (60) (024). The mean of 11 electron microprobe analyses gave elemental concentrations as follows: Pb 10.09(1) wt.%, Tl 20.36(1), Sb 23.95(1), As 21.33(8), S 26.16(8), totalling 101.95 wt.%, corresponding to Tl4.15Pb2.03(As11.86Sb8.20)S34. The new mineral is named for Alberto Dal Negro, Professor in Mineralogy and Crystallography at the University of Padova since 1976.


Corresponding author


Hide All
Burri, G., Graeser, S., Marumo, F. and Nowacki, W. (1965) Imhofit, ein neues thallium-arsensulfosalzaus dem Lengenbach (Binnatal, Kt. Wallis). Chimia, 19, 499500.
Graeser, S. and Edenharter, A. (1997) Jentschite (TlPbAs2SbS6); a new sulphosalt mineral from Lengenbach, Binntal (Switzerland). Mineralogical Magazine, 61, 131137.
Graeser, S. and Schwander, H. (1992) Edenharterite (TlPbAs3S6): a new mineral from Lengenbach, Binntal (Switzerland). European Journal of Mineralogy, 4, 12651270.
Graeser, S., Berlepsch, P., Makovicky, E. and Balić-Žunić, T. (2001) Sicherite, TlAg2(As,Sb)3S6, a new sulfosalt mineral from Lengenbach (Binntal, Switzerland): description and structure determination. American Mineralogist, 86, 10871093.
Graeser, S., Topa, D., Balić-Žunić, T. and Makovicky, E. (2006) Gabrielite, Tl2AgCu2As3S7, a new species of thallium sulfosalt from Lengenbach, Binntal, Switzerland. The Canadian Mineralogist, 44, 135140.
Graeser, S., Cannon, R., Drechser, E., Raber, T. and Roth, P. (2008) Faszination Lengenbach abbau - Forschung- Mineralien 1958-2008. Kristallographik Verlag, Achberg, 192 pp.
Hofmann, B.A. and Knill, M.D. (1996) Geochemistry and genesis of the Lengenbach Pb-Zn-As-Tl-Ba- mineralisation, Binn Valley, Switzerland. Mineralium Deposita, 31, 319339.
Johan, Z., Mantienne, J. and Picot, P. (1981) La chabournéite, un nouveau mineral thallifere. Bulletin de Mineralogie, 104, 1015.
Knill, M. (1996) The Pb-Zn-As-Tl-Ba-deposit at Lengenbach, Binn Valley, Switzerland. Beitrage zur Geologie der Schweiz, Geotechnische Serie 90; Hrsg.: Schweizerische Geotechnische Kommission, 74 pp.
Moelo, Y., Makovicky, E., Mozgova, N.N., Jambor, J.L., Cook, N., Pring, A., Paar, W., Nickel, E.H., Graeser, S., Karup-Møller, S., Balić-Žunić, T., Mumme, W.G., Vurro, F., Topa, D., Bindi, L., Bente, K. and Shimizu, M. (2008) Sulfosalt systematics: a review. Report of the sulfosalt sub-committee of the IMA Commission on Ore Mineralogy. European Journal of Mineralogy, 20, 746.
Nagl, A. (1979) The crystal structure of a thallium sulfosalt, Tl8Pb4Sb21As19S68 . Zeitschrift fur Kristallographie, 150, 85106.
Werner, P.E., Eriksson, L. and Westdahl, M. (1985) TREOR, a semi-exhaustive trial-and-error powder indexing program for all symmetries. Journal of Applied Crystallography, 18, 367370.


Dalnegroite, Tl5–x Pb2x (As,Sb)2l–x S34, a new thallium sulphosalt from Lengenbach quarry, Binntal, Switzerland

  • F. Nestola (a1), A. Guastoni (a1), L. Bindi (a2) and L. Secco (a1)


Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed