Mummeite

Cu0.58Ag3.11Pb1.10Bi6.65S13
IMA status
  • Approved
IMA symbol
Mum
Discovered
1986
Also known as
  • IMA1986-025
  • Mummeiet

Where it forms, where it's found

Type locality
Acapulco adit
  1. Alaska Mine
  2. Poughkeepsie Gulch
  3. San Juan County
  4. Colorado
  5. USA

37.9311°, -107.6294°

7recorded occurrences
Source · OpenStreetMap

Safety & handling

Physical

Hardness
123456789104/ 10 MOHS
  1. 1Talc
  2. 2Gypsum
  3. 3Calcite
  4. 4Fluorite
  5. 5Apatite
  6. 6Orthoclase
  7. 7Quartz
  8. 8Topaz
  9. 9Corundum
  10. 10Diamond
Transparency
Opaque
Colour
Gray
Density
6.795 g/cm³

Optical

Anisotropism
Pronounced, gray to brownish yellow to dark indigo
Bireflectance
Perceptible
Tropism
Anisotropic
Reflectance R%
(43.3,47.5) 470, (42.8,47.0) 546, (42.5,46.4) 589, (42.2,45.7) 650
Reflected-light panel
R̄ 42.7 %anisotropic · dual curve
Specimen sRGB 231, 162, 91
White reference100 % reflector under same lamp
R₁ R₂
Mode
Bireflectance
Perceptible
Anisotropism
Pronounced, gray to brownish yellow to dark indigo

Crystallography

Crystal system
Monoclinic
Cell parameters
a = 13.47(1) Å · b = 4.06(1) Å · c = 21.63(1) Å
Cell angles
β = 92.9(1) °
Ratio a:b:c
1 : 0.301 : 1.606
Morphology

Massive, granular, lath-like.

Twinning

Along a composition plane parallel to elongation.

Type-locality form

Intergrowths of short columnar crystals to 1 mm.

Comment

Suggested space groups: C2/m or Cm (Karup-Møller & Makovicky, 1992). "Cuproplumbian mummeite" has a = 13.48(1), b = 4.06(1), c = 21.72(1) A, β = 93.9(1)° (Karup-Møller & Makovicky, 1992). A sample from the Mike mine has: a = 13.41, b = 4.05, c = 21.51 Å, β = 94.5° (Mumme, 1990). Synthetic Ag3.5Bi7.5S13 has space group C2/m, a = 13.3237(2), b = 4.0455(4), c = 21.484(3) Å, β = 92.90 (1)° (Poudeu Poudeu and Ruck, 2005).

Chemical composition

Constituent elements
Mass composition breakdown
ElementAtoms At. mass g/mol Mass g/molMass share
83BiBismuthBismuth6.65208.9801389.717
57.74%
16SSulfurSulfur1332.060416.780
17.32%
47AgSilverSilver3.11107.868335.469
13.94%
82PbLeadLead1.1207.200227.920
9.47%
29CuCopperCopper0.5863.54636.857
1.53%
Total2406.743100.00%

Mass share = atoms × atomic mass ÷ molar mass × 100

From IMA formula

Synonyms

  • IMA1986-025
  • Mummeiet

In other languages

German
IMA 1986-025 · Mummeit
Italian
Mummeite

Classification

Strunz
10th ed.

2.JA.05f

  • 2Sulfides and SulfosaltsClass
  • 2.JSulfosalts of PbS archetypeDivision
  • 2.JAGalena derivatives with little or no PbGroup
  • 2.JA.05fMummeiteSpecies
Dana
8th ed.

03.08.10.04

  • 03SulfosaltsClass
  • 03.081 < ø < 2Type
  • 03.08.10Pavonite Group (Monoclinic: C/2c bismuth sulfosalts)Group
  • 03.08.10.04MummeiteSpecies

Group, growth & confusion

In the same group
12 members

Literature, links & citation

Citations
  1. 1990Mumme, W.G. (1990): A note on the occurrence, composition and crystal structures of pavonite homologous series members 4P, 6P, and 8P. Neues Jahrbuch für Mineralogie, Monatshefte 1990, 193-204. (as unnamed 8P member) [Abs. in American Mineralogist 76 (1991) 665-671]
  2. 1992Karup-Møller, S., Makovicky, E. (1992) Mummeite - A new member of the pavonite homologous series from Alaska mine, Colorado. Neues Jahrbuch für Mineralogie - Monatshefte, 1992. 555-576
  3. 1997Mandarino, Joseph A. (1997) New Minerals 1990-1994. The Mineralogical Record Inc., Tuscon, Arizona. 220pp.
  4. 2005Poudeu Poudeu, P.F. and Ruck, M. (2005): Ag3.5Bi7.5S13, a new member (N = 8) of the homologous series [Bi2S3]2·[AgBiS2](N−1)/2. Acta Crystallographica C61, i41-i43. [synthetic, Cu-free sample]
  5. 2005(2005) Mummeite. Handbook of Mineralogy. Mineralogical Society of America
Cite this entry
@misc{mineral2026,
  author    = {Mineral Index editorial board},
  title     = {Mummeite — Mineral Index},
  year      = {2026},
  url       = {https://mineralindex.org/minerals/mummeite-2807},
  note      = {Accessed 2026-05-11}
}