Thalfenisite

Tl6(Fe,Ni)25S26Cl
IMA status
  • Approved
IMA symbol
Tfn
Discovered
1979
IMA approved
1979
Also known as
  • IMA1979-018
  • Thalfenisiet

Where it forms, where it's found

Type locality
Oktyabrsky Mine
  1. Talnakh Cu-Ni Deposit
  2. Norilsk-Talnakh Mining Region
  3. Taimyr Peninsula
  4. Taymyrskiy Autonomous Okrug
  5. Krasnoyarsk Krai
  6. Russia

69.5248°, 88.3401°

1recorded occurrences
Source · OpenStreetMap

Safety & handling

Physical

Hardness
123456789101 – 1.5/ 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
Brown
Tenacity
brittle
Density
5.26 g/cm³

Optical

Optical type
Isotropic
Optical colour
Brown in reflected light, dark brown in oil
Reflectance R%
(23.6) 440, (25.6) 560, (27.3) 600, (30.3) 680
Reflected-light panel
R̄ 26.7 %isotropic · single curve
Specimen sRGB 193, 127, 66
White reference100 % reflector under same lamp
Reflected colour
Brown in reflected light, dark brown in oil

Crystallography

Crystal system
Isometric
Cell parameters
a = 10.29(2) Å
Z
1
Type-locality form

As grains, to 5 µm, in aggregates.

Comment

Point Group: n.d.; Space Group: n.d.

Chemical composition

Constituent elements
Mass composition breakdown
ElementAtoms At. mass g/mol Mass g/molMass share
28NiNickelNickel2558.6931467.325
29.59%
26FeIronIron2555.8451396.125
28.15%
81TlThalliumThallium6204.3801226.280
24.73%
16SSulfurSulfur2632.060833.560
16.81%
17ClChlorineChlorine135.45035.450
0.72%
Total4958.740100.00%

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

From IMA formula

Impurities
  • K

Synonyms

  • IMA1979-018
  • Thalfenisiet

In other languages

German
IMA 1979-018 · Thalfenisit
Italian
Thalfenisite
Russian
талфенизит

Classification

Strunz
10th ed.

2.FC.05

  • 2Sulfides and SulfosaltsClass
  • 2.FSulfides of arsenic, alkalies; sulfides with halide, oxide, hydroxide, H2ODivision
  • 2.FCWith Cl, Br, I (halide-sulfides)Group
  • 2.FC.05ThalfenisiteSpecies
Dana
8th ed.

02.15.02.02

  • 02SulfidesClass
  • 02.15Chlor-sulfidesType
  • 02.15.02Djerfisherite GroupGroup
  • 02.15.02.02ThalfenisiteSpecies
CIM
—

6.5.12

  • 6Sulphosalts - Sulphostannates, Sulphogermanates,Sulpharsenates, Sulphantimonates, Sulphovanadates and SulphohalidesClass
  • 6.5SulphohalidesGroup
  • 6.5.12ThalfenisiteSpecies

Group, growth & confusion

In the same group
4 members

Literature, links & citation

Citations
  1. 1979Rudashevskii, N.S., Karpenov, A.M., Shipova, G.S., Shishkin, N.N., Ryabkin, V.A. (1979) Thalfenisite, the thallium analogue of djerfisherite. Zapiski Vsesoyuznogo Mineralogicheskogo Obshchestva: 108(6): 696-701.
  2. 1981Fleischer, Michael, Chao, George Y., Francis, Carl A., Pabst, and Adolf (1981) New Mineral Names. American Mineralogist, 66 (1-2) 217-220
  3. 1997Barkov, A.Y., Laajoki, K.V.O., Gehör, S.A., Yakovlev, Y.N., Taikina-Aho, O. (1997) Chlorine-poor analogues of djerfisherite - thalfenisite from Noril'sk, Siberia and Salmagorsky, Kola Peninsula, Russia. The Canadian Mineralogist: 35: 1421-1430.
  4. 1999Jambor, J.L. and Roberts, A.C. (1999) New mineral names. American Mineralogist: 84: 193-198.
  5. 2005(2005) Thalfenisite. Handbook of Mineralogy. Mineralogical Society of America
Cite this entry
@misc{mineral2026,
  author    = {Mineral Index editorial board},
  title     = {Thalfenisite — Mineral Index},
  year      = {2026},
  url       = {https://mineralindex.org/minerals/thalfenisite-3932},
  note      = {Accessed 2026-05-11}
}