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Markwelchite

A valid IMA mineral species
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Formula:
TlPbSbS3
Colour:
black
Lustre:
Metallic
Hardness:
3 - 4
Specific Gravity:
6.696 (Calculated)
Crystal System:
Monoclinic
Name:
The name markwelchite honors Dr Mark D. Welch (b. 1960) of the Natural History Museum, London, United Kingdom. Dr. Welch is a well-known mineralogical crystallographer who has researched a wide range of minerals, many of which have complex structures and unusual crystal chemistry.
The Sb analogue of richardsollyite.
It is isostructural with three synthetic compounds, i.e., KEuAsS3, RbEuAsS3, and CsEuAsS3.


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Unique IdentifiersHide

Mindat ID:
471106
Long-form identifier:
mindat:1:1:471106:9

IMA Classification of MarkwelchiteHide

Classification of MarkwelchiteHide

Strunz-mindat (2026):
2.HD.15

2 : SULFIDES and SULFOSALTS (sulfides, selenides, tellurides; arsenides, antimonides, bismuthides; sulfarsenites, sulfantimonites, sulfbismuthites, etc.)
H : Sulfosalts of SnS archetype
D : With Tl

Mineral SymbolsHide

As of 2021 there are now IMA–CNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.

SymbolSourceReference for Standard
MrwIMA–CNMNCWarr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43

Physical Properties of MarkwelchiteHide

Lustre:
Metallic
Transparency:
Opaque
Colour:
Black
Streak:
Black
Hardness:
3 - 4 on Mohs scale
Hardness:
VHN15=188 - 218 kg/mm2 - Vickers
Cleavage:
None Observed
Fracture:
Irregular/Uneven
Density:
6.696 g/cm3 (Calculated)

Optical Data of MarkwelchiteHide

Anisotropism:
grayish white to bluish tint rotation tints
Reflectivity:
WavelengthR1 (%)R2 (%)
471nm28.5% 31.5%
548nm28.3% 30.7%
586nm27.9% 30.3%
652nm27.6% 29.8%


Graph shows reflectance levels at different wavelengths (in nm). Peak reflectance is 31.5%.
R1 shown in black, R2 shown in red
Colour in reflected light:
grey
Internal Reflections:
bright red

Chemistry of MarkwelchiteHide

Mindat Formula:
TlPbSbS3
Element Weights:
Element% weight
Pb32.913 %
Tl32.466 %
Sb19.341 %
S15.280 %

Calculated from ideal end-member formula.
Pb
Tl
Sb
S
Elements listed:
Pb, S, Sb, Tl - search for minerals with similar chemistry

Crystallography of MarkwelchiteHide

Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
P21/c
Setting:
P21/c
Cell Parameters:
a = 8.9144(3) Å, b = 8.4513(3) Å, c = 8.6511(3) Å
β = 108.723(4)°
Ratio:
a:b:c = 1.055 : 1 : 1.024
Unit Cell V:
617.27 ų (Calculated from Unit Cell)
Z:
4

X-Ray Powder DiffractionHide

Type Occurrence of MarkwelchiteHide

Type Locality:
ⓘ Jas Roux, La Chapelle-en-Valgaudemar, Gap, Hautes-Alpes, Provence-Alpes-Côte d'Azur, France
General Appearance of Type Material:
anhedral crystals up to 40 microns in size
Place of Conservation of Type Material:
Type material is deposited in the collections of the Natural History Museum, University of Florence, Via La Pira 4, I-50121 Firenze, Italy, catalogue number 3739
Geological Setting of Type Material:
a hydrothermal stratiform deposit hosted in dolomitic metalimestones of Triassic age and appears as several sedimentary lenses embedded in the Pigeonnier anatexites.
Associated Minerals at Type Locality:
GuettarditePierrotiteProtochabournéiteRealgarStibnite
Twinnite
Reference:
Bindi, Luca; Biagioni, Cristian; Förster, Hans-Jürgen; Adelmann., Holger Georg (2024) Markwelchite, TlPbSbS3, a new Tl–Pb sulfosalt from the hydrothermal deposit of Jas Roux, Hautes-Alpes, France. Mineralogical Magazine, 88 (4). 503-509

Synonyms of MarkwelchiteHide

Other Language Names for MarkwelchiteHide

Related Minerals - Strunz-mindat GroupingHide

2.HD.EnneasartoriteTl6Pb32As70S140Mon. 2/m : P21/c
2.HD.ShimeniteTl5Sb21-yAsyS34Tric. 1 : P1
2.HD.DewititeAgzTl10-x-zPb2xSb42-x-yAsyS68Tric. 1 : P1
2.HD.BuyniteTlPb14As17S40Mon. 2 : P21
2.HD.VallouiseiteAg3Tl21.5PbSb63As41.5S170Tric. 1 : P1
2.HD.GiuşcăiteAg2Tl4Pb4As20Sb2S40Mon. m
2.HD.BoscardiniteTlPb4(Sb7As2)S18Tric. 1 : P1
2.HD.GungeriteTlAs5Sb4S13Orth. mmm(2/m2/m2/m) : Pbcn
2.HD.05eDalnegroite(Tl4Pb2)(As12Sb8)S34Tric. 1 : P1
2.HD.05LoránditeTlAsS2Mon. 2/m : P21/c
2.HD.05WeissbergiteTlSbS2Tric. 1 : P1
2.HD.05eChabournéiteAgzTl8-x-zPb4+2xSb40-x-yAsyS68 with 0.00 < x < 0.40(9), 16.15(3)< y < 19.11(10), 0.04(4) < z < 0.11(6)Tric. 1 : P1
2.HD.15ChristiteTlHgAsS3Orth. mmm(2/m2/m2/m) : Cmca
2.HD.15RichardsollyiteTlPbAsS3Mon. 2/m : P21/c
2.HD.20JankovićiteTl5Sb9(As,Sb)4S22Tric. 1 : P1
2.HD.25RebuliteTl5Sb5As8S22Mon. 2/m : P21/c
2.HD.30ImhofiteTl5.8As15.4S26Mon. 2/m : P21/c
2.HD.35EdenharteritePbTlAs3S6Orth. mm2 : Fdd2
2.HD.40JentschiteTlPbAs2SbS6Mon. 2/m : P21/c
2.HD.45ProtochabournéiteTl4-xPb2+2xSb20-x-yAsyS34 with 0.02(2) <= x <= 0.34(2), 5.71(9) <= y <= 6.69(9)Tric. 1 : P1
2.HD.45HutchinsoniteTlPbAs5S9Orth. mmm(2/m2/m2/m) : Pbca
2.HD.50BernarditeTlAs5S8Mon. 2/m : P21/c
2.HD.55SicheriteTlAg2(As,Sb)3S6Orth.
2.HD.55GeueriteAg2Tl4Pb4As22S40Mon. 2/m : P21/c
2.HD.60GabrieliteTl6Ag3Cu6(As,Sb)9S21Tric. 1 : P1
2.HD.65TsygankoiteMn8Tl8Hg2(Sb21Pb2Tl)S48Mon. 2/m : B2/m
2.HD.70DrechsleriteTl4(Sb4-xAsx)S8 (1 < x < 2)Tric. 1 : P1

Other InformationHide

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 MarkwelchiteHide

References for MarkwelchiteHide

Localities for MarkwelchiteHide

Showing 1 localities.

This map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.
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Locality ListHide

- This locality has map coordinates listed. - This locality has estimated coordinates. ⓘ - 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). Struck out - Mineral was erroneously reported from this locality. Faded * - Never found at this locality but inferred to have existed at some point in the past (e.g. from pseudomorphs).

All localities listed without proper references should be considered as questionable.
France (TL)
 
  • Provence-Alpes-Côte d'Azur
    • Hautes-Alpes
      • Gap
        • La Chapelle-en-Valgaudemar
Bindi et al. (2024) +1 other reference
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