Lengenbachite
A valid IMA mineral species - grandfathered
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About Lengenbachite
Formula:
Ag4Cu2Pb18As12S39
Colour:
Steel-gray, iridescent tarnish at times
Lustre:
Metallic
Hardness:
1½ - 2
Specific Gravity:
5.8 - 5.85
Crystal System:
Triclinic
Name:
From the type locality, the Lengenbach quarry, Binntal, Valais, Switzerland.
Type Locality:
This page provides mineralogical data about Lengenbachite.
Unique Identifiers
Mindat ID:
2373
Long-form identifier:
mindat:1:1:2373:9
GUID
(UUID V4):
(UUID V4):
73b6399f-32e4-4250-b52b-ee4114294c2e
IMA Classification of Lengenbachite
Approved, 'Grandfathered' (first described prior to 1959)
IMA Formula:
Ag4Cu2Pb18As12S39
First published:
1904
Type description reference:
Classification of Lengenbachite
2.HF.30
2 : SULFIDES and SULFOSALTS (sulfides, selenides, tellurides; arsenides, antimonides, bismuthides; sulfarsenites, sulfantimonites, sulfbismuthites, etc.)
H : Sulfosalts of SnS archetype
F : With SnS and PbS archetype structure units
2 : SULFIDES and SULFOSALTS (sulfides, selenides, tellurides; arsenides, antimonides, bismuthides; sulfarsenites, sulfantimonites, sulfbismuthites, etc.)
H : Sulfosalts of SnS archetype
F : With SnS and PbS archetype structure units
3.3.7.1
3 : SULFOSALTS
3 : 3 <Ăž < 4
3 : SULFOSALTS
3 : 3 <Ăž < 4
5.7.40
5 : Sulphosalts - Sulpharsenites and Sulphobismuthites (those containing Sn, Ge,or V are in Section 6)
7 : Sulpharsenites etc. of Pb and other metals
5 : Sulphosalts - Sulpharsenites and Sulphobismuthites (those containing Sn, Ge,or V are in Section 6)
7 : Sulpharsenites etc. of Pb and other metals
Mineral Symbols
As of 2021 there are now IMAâCNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.
| Symbol | Source | Reference |
|---|---|---|
| Len | IMAâCNMNC | Warr, L.N. (2021). IMAâCNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43 |
Physical Properties of Lengenbachite
Metallic
Transparency:
Opaque
Colour:
Steel-gray, iridescent tarnish at times
Streak:
Brown-Black
Hardness:
1½ - 2 on Mohs scale
Hardness:
VHN100=35 - Vickers
Tenacity:
Malleable
Cleavage:
Perfect
Perfect on {100}; two others across the flat {100}
face.
Perfect on {100}; two others across the flat {100}
face.
Density:
5.8 - 5.85 g/cm3 (Measured) 5.78 g/cm3 (Calculated)
Optical Data of Lengenbachite
Anisotropism:
Weak
Reflectivity:
| Wavelength | R1 | R2 |
|---|---|---|
| 400nm | 38.9% | 40.0% |
| 420nm | 38.5% | 39.8% |
| 440nm | 38.2% | 39.4% |
| 460nm | 37.6% | 39.0% |
| 480nm | 37.3% | 38.7% |
| 500nm | 36.8% | 38.3% |
| 520nm | 36.3% | 37.9% |
| 540nm | 35.9% | 37.4% |
| 560nm | 35.5% | 36.9% |
| 580nm | 35.3% | 36.5% |
| 600nm | 35.1% | 36.1% |
| 620nm | 34.7% | 35.7% |
| 640nm | 34.2% | 35.2% |
| 660nm | 33.5% | 34.4% |
| 680nm | 32.8% | 33.7% |
| 700nm | 32.0% | 32.9% |
Graph shows reflectance levels at different wavelengths (in nm). Top of box is 100%. Peak reflectance is 40.0%.
R1 shown in black, R2 shown in red
Chemistry of Lengenbachite
Mindat Formula:
Ag4Cu2Pb18As12S39
Common Impurities:
Fe,Sb
Crystallography of Lengenbachite
Crystal System:
Triclinic
Twinning:
On {100}; twin lamellae seen in polished section.
Comment:
Point Group: 1 or 1; Two subcells are recognized: the first (pseudotetragonal) has a = 36.892(20) b = 5.842(5) c = 5.847(5) α = 90.00⊠ÎČ = 92.00⊠γ = 91.01(1)⊠Z = 6 and the second (pseudohexagonal) has a = 36.892(20) b = 3.895(4) c = 6.378(7) α = 90.00⊠ÎČ = 90.00⊠γ = 91.01(1)⊠Z=6
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 3.06 Ă | (100) |
| 2.84 Ă | (90) |
| 4.60 Ă | (30) |
| 2.93 Ă | (20) |
| 2.04 Ă | (20) |
| 9.31 Ă | (10) |
| 7.69 Ă | (10) |
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| High-đ alteration and/or metamorphism | |
| 33 : Minerals deposited by hydrothermal metal-rich fluids (see also [#12]) |
Type Occurrence of Lengenbachite
Place of Conservation of Type Material:
n.d.
Associated Minerals at Type Locality:
Reference:
Solly, R.H. (1904) Various minerals from the Lengenbach quarry. Nature: 71: 118.
Other Language Names for Lengenbachite
German:Lengenbachit
Spanish:Lengenbachita
Common Associates
Associated Minerals Based on Photo Data:
| 31 photos of Lengenbachite associated with Pyrite | FeS2 |
| 31 photos of Lengenbachite associated with Jordanite | Pb14As6S23 |
| 26 photos of Lengenbachite associated with Dolomite | CaMg(CO3)2 |
| 14 photos of Lengenbachite associated with Sphalerite | ZnS |
| 7 photos of Lengenbachite associated with Realgar | As4S4 |
| 6 photos of Lengenbachite associated with Tennantite Subgroup | Cu6(Cu4C2+2)As4S12S |
| 5 photos of Lengenbachite associated with Dufrénoysite | Pb2As2S5 |
| 4 photos of Lengenbachite associated with Marcasite | FeS2 |
| 2 photos of Lengenbachite associated with Smithite | AgAsS2 |
| 2 photos of Lengenbachite associated with Wurtzite | (Zn,Fe)S |
Related Minerals - Strunz-mindat Grouping
| 2.HF. | Ramosite | Pb25.7Sn8.3Mn3.4Sb6.4S56.2 |
| 2.HF.20 | Vrbaite | Hg3Tl4As8Sb2S20 |
| 2.HF.25a | Cylindrite | Pb3Sn4FeSb2S14 |
| 2.HF.25b | Franckeite | Fe2+(Pb,Sn2+)6Sn4+2Sb2S14 |
| 2.HF.25a | LĂ©vyclaudite | Pb8Sn7Cu3(Bi,Sb)3S28 |
| 2.HF.25b | PotosĂite | Pb6Sn3FeSb3S16 |
| 2.HF.25b | Coiraite | (Pb,Sn)12.5Sn5FeAs3S28 |
| 2.HF.25a | Abramovite | Pb2SnInBiS7 |
| 2.HF.25b v | Plumbostannite | Pb2Fe2Sn2Sb2S11 |
| 2.HF.25a | Merelaniite | Mo4Pb4VSbS15 |
Other Information
Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.
Internet Links for Lengenbachite
mindat.org URL:
https://www.mindat.org/min-2373.html
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External Links:
References for Lengenbachite
Reference List:
Localities for Lengenbachite
symbol to view information about a locality.
The Locality List
- This locality has map coordinates listed.
- This locality has estimated coordinates.
â - Click for references and further information on this occurrence.
? - Indicates mineral may be doubtful at this locality.
- Good crystals or important locality for species.
- World class for species or very significant.
(TL) - Type Locality for a valid mineral species.
(FRL) - First Recorded Locality for everything else (eg varieties).
All localities listed without proper references should be considered as questionable.
Canada | |
| RIDLAND (1941) +1 other reference |
| RIDLAND (1941) | |
Russia | |
| G.I. Shvedov et al. (2019) |
Switzerland (TL) | |
| Nature (1904) +1 other reference |
| 50. (in German) +1 other reference |
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Lengenbach Quarry, FĂ€ld, Binn, Goms, Valais, Switzerland