Dufrenoysite Mineral Data

Dufrenoysite Mineral Data +

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General Dufrenoysite Information

Chemical Formula:

Pb2As2S5

Composition:

Molecular Weight = 724.57 gm

Arsenic 20.68 % As

Lead 57.19 % Pb

Sulfur 22.13 % S

______

100.00 %

Empirical Formula:

Pb₂As₂S₅

Environment:

An uncommon mineral of moderate to low-temperature hydrothermal origin.

IMA Status:

Valid Species (Pre-IMA) 1845

Locality:

Binnental, Valais, Switzerland. Link to MinDat.org Location Data.

Name Origin:

For Ours Pierre Armand Petit Dufrenoy (1792-1857), French mineralogist, National School of Mines, Paris, France.

Synonym:

ICSD 18122

PDF 10-453

Dufrenoysite Image

Images:

Dufrenoysite

Comments: Black prismatic crystal of Dufrenoysite with brassy yellow pyrite on succroidal dolomite.
Location: Lengenbach quarry, Binntal, Valais, Switzerland. Scale: Not Given.
© Lou Perloff / Photo Atlas of Minerals

Images:

Dufrenoysite

Comments: Single, black dufr?noysite crystal in a vug in white dolomite.
Location: Lengenbach quarry, Binntal, Valais, Switzerland. Scale: Crystal size 2.5 mm.
© Walter Gabriel

Dufrenoysite Crystallography

Axial Ratios:

a:b:c =0.3253:1:0.3048

Cell Dimensions:

a = 8.41, b = 25.85, c = 7.88, Z = 8; beta = 90.5° V = 1,713.03 Den(Calc)= 5.62

Crystal System:

Monoclinic - PrismaticH-M Symbol (2/m) Space Group: P 2₁/m

$Help on X Ray Diffraction:$ X Ray Diffraction:

By Intensity(I/I_o): 3.74(1), 3(0.9), 2.7(0.8),

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Forms: [ 0 5 2] [ 2 3 2] [ 0 1 0] [ 0 1 1] [ 2 1 0] [ 2 1 2] [ 1 2 1] [ 0 2 1] [ 2 3 0] [ 2 3 2] [ 1 0 0] [ 1 1 0] [ 1 0 1] [ 1 2 0] [ 0 0 1]

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Crystal Structure:

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Marumo F , Nowacki W , Zeitschrift fur Kristallographie , 124 (1967) p.409-419, The crystal structure of dufrenoysite, Pb16As16S40, Locality: Lengenbach, Binnatal, Switzerland

View Additional jPOWD Structure files for Dufrenoysite
[1]

Physical Properties of Dufrenoysite

Cleavage:

[010] Perfect

Color:

Lead gray, Gray, Steel gray.

Density:

5.55 - 5.57, Average = 5.56

Diaphaniety:

Subtranslucent to opaque

Fracture:

Brittle - Conchoidal - Very brittle fracture producing small, conchoidal fragments.

Habit:

Massive - Uniformly indistinguishable crystals forming large masses.

Hardness:

3 - Calcite

Luster:

Sub Metallic

Streak:

red brown

Optical Properties of Dufrenoysite

Optical Data:

Biaxial (?), b=2.71

Pleochroism (y):

dark brownish red.

RL Anisotrophism:

Strong, in brown-violet and dark green colors.

RL Color:

White, sometimes showing deep red internal reflections.

RL Pleochroism:

Very weak.

Reflectivity

**Standardized Intensity (100%) Reflection Spectra of Dufrenoysite in Air**
λ	R₁	R₂	∑ R₁(λ)	∑ R₂(λ)
400 nm	38.70	42.10
420 nm	38.50	41.90
440 nm	38.30	41.70
460 nm	38.00	41.40
480 nm	37.70	41.00
500 nm	37.30	40.60
520 nm	36.90	40.10
540 nm	36.30	39.60
560 nm	35.70	38.90
580 nm	35.00	38.00
600 nm	34.00	37.10
620 nm	33.20	36.10
640 nm	32.30	35.20
660 nm	31.60	34.30
680 nm	30.90	33.50
700 nm	30.30	32.70

**Calculated Relative Intensity Colors of Dufrenoysite in Air**
Relative Intensity	0%	30%	60%	90%	100%	120%	150%	180%	210%	240%	270%
R₁
R₂

Calculated Properties of Dufrenoysite

Electron Density:

r_electron=4.81 gm/cc
note: r_Dufrenoysite=5.62 gm/cc.

Fermion Index

Fermion Index = 0.12805
Boson Index = 0.87195

Photoelectric:

PE_Dufrenoysite=1,042.99 barns/electron
U=PE_Dufrenoysite x r_electron=5,015.65 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Dufrenoysite is Not Radioactive

Dufrenoysite Classification

Dana Class:

3.5.9.3 (3)Sulfides - Sulfosalts

(3.5)where 2.5 < z/y < 3 - (A+)i (A++)j [By Cz], A=metals, B=semi-metals, C=non-metals

(3.5.9)Dana Group

3.5.9.1 Cosalite Pb2Bi2S5 Pbnm 2/m 2/m 2/m

3.5.9.2 Veenite Pb2(Sb,As)2S5 P 2₁cn mm2

3.5.9.3 Dufrenoysite Pb2As2S5 P 2₁/m 2/m

Strunz Class:

II/E.18-10 II - Sulfides and sulphosalts

II/E - Sulfosalts (S : As,Sb,Bi = x) Lead-Sulfosalts with As/Sb, x=3,0-2,5

II/E.18 - Dufrenoysite - Veenite series

II/E.18-10 Dufrenoysite Pb2As2S5 P 2₁/m 2/m

II/E.18-20 Veenite Pb2(Sb,As)2S5 P 2₁cn mm2

Other Dufrenoysite Information

References:

NAME( AntBidBlaNic1) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(AntBidBlaNic1)

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Dufrenoysite

Pb2As2S5
Dana No: 3.5.9.3 Strunz No: II/E.18-10
Locality:

Notes: