Tetradymite Mineral Data

Tetradymite Mineral Data +

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General Tetradymite Information

Chemical Formula:

Bi2Te2S

Composition:

Molecular Weight = 705.23 gm

Bismuth 59.27 % Bi

Tellurium 36.19 % Te

Sulfur 4.55 % S

______

100.00 %

Empirical Formula:

Bi₂Te₂S

Environment:

Found in hydrotherma quartz-gold veins o f moderate to high temperature and contact metamorphic deposits.

IMA Status:

Valid Species (Pre-IMA) 1831

Locality:

Zupkov (Zsubkó, Schubkau), Stredoslovenský Kraj, Slovak Republic. Link to MinDat.org Location Data.

Name Origin:

From the Greek, tetradymos, "fourfold."

Synonym:

Csiklovaite

ICSD 26720

PDF 42-1447

Tetradymite Image

Images:

Tetradymite

Comments: Gray metallic foliated tetradymite in quartz.
Location: Mangfallberg, Boliden, Vasterbotten, Sweden. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Tetradymite Crystallography

Axial Ratios:

a:c = 1:6.98166

Cell Dimensions:

a = 4.2381, c = 29.589, Z = 3; V = 460.26 Den(Calc)= 7.63

Crystal System:

Trigonal - Hexagonal ScalenohedralH-M Symbol (3 2/m) Space Group: R 3m

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

By Intensity(I/I_o): 2.292(1), 3.1(1), 2.111(0.75),

Forms:

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Forms: [ 0 1 2] [ 1 0 1] [ 0 0 1]

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Crystal Structure:

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Pauling L , American Mineralogist , 60 (1975) p.994-997, The formula, structure, and chemical bonding of tetradymite, Bi14Te13S8, and the, Phase Bi14Te15S6, cell parameters were computed from those provided in the rhombohedral setting

View Additional jPOWD Structure files for Tetradymite
[1]

Physical Properties of Tetradymite

Cleavage:

[0001] Perfect

Color:

Steel gray, Yellow gray.

Density:

7.2 - 7.9, Average = 7.55

Diaphaniety:

Opaque

Fracture:

Uneven - Flat surfaces (not cleavage) fractured in an uneven pattern.

Habit:

Granular - Generally occurs as anhedral to subhedral crystals in matrix.

Habit:

Lamellar - Thin laminae producing a lamellar structure.

Habit:

Pseudo Hexagonal - Crystals show a hexagonal outline.

Hardness:

1.5-2 - Talc-Gypsum

Luminescence:

None.

Luster:

Metallic

Magnetism:

Nonmagnetic

Streak:

steel gray

Optical Properties of Tetradymite

RL Anisotrophism:

Weak.

RL Color:

White.

Reflectivity

**Standardized Intensity (100%) Reflection Spectra of Tetradymite in Air**
λ	R₁	R₂	∑ R₁(λ)	∑ R₂(λ)
400 nm	50.00	52.70
420 nm	50.80	53.60
440 nm	51.60	54.50
460 nm	52.00	55.00
480 nm	52.40	55.40
500 nm	52.70	55.80
520 nm	53.00	56.20
540 nm	53.20	56.40
560 nm	53.30	56.50
580 nm	53.40	56.60
600 nm	53.50	56.70
620 nm	53.50	56.80
640 nm	53.40	56.90
660 nm	53.40	57.00
680 nm	53.40	57.10
700 nm	53.50	57.20

**Calculated Relative Intensity Colors of Tetradymite in Air**
Relative Intensity	0%	20%	40%	60%	80%	100%	120%	140%	160%	170%
R₁
R₂

Calculated Properties of Tetradymite

Electron Density:

r_electron=6.19 gm/cc
note: r_Tetradymite=7.63 gm/cc.

Fermion Index

Fermion Index = 0.02925
Boson Index = 0.97075

Photoelectric:

PE_Tetradymite=1,313.02 barns/electron
U=PE_Tetradymite x r_electron=8,125.77 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Tetradymite is Not Radioactive

Tetradymite Classification

Dana Class:

2.11.7.1 (2)Sulfides - Including Selenides and Tellurides

(2.11)where Am Bn Xp, with (m+n):p=2:3

(2.11.7)Tetradymite Group (Trigonal: R-3m)

2.11.7.1 Tetradymite Bi2Te2S R 3m 3 2/m

2.11.7.2 Tellurobismuthite Bi2Te3 R 3m 3 2/m

2.11.7.3 Tellurantimony Sb2Te3 R 3m 3 2/m

2.11.7.4 Paraguanajuatite Bi2(Se,S)3 R 3m 3 2/m

2.11.7.5 Kawazulite Bi2(Te,Se,S)3 R 3m 3 2/m

2.11.7.6 Skippenite Bi2Se2(Te,S) R 3m 3 2/m

Strunz Class:

II/D.09-60 II - Sulfides and sulphosalts

II/D - Sulfides with metal: sulfur, selenium and tellurium < 1:1, Tellurides with Copper, Silver, Gold

II/D.09 - Tetradymite group, Tellurantimony - Kawazulite series

II/D.09-10 Tellurantimony Sb2Te3 R 3m 3 2/m

II/D.09-20 Tellurobismuthite Bi2Te3 R 3m 3 2/m

II/D.09-30 Paraguanajuatite Bi2(Se,S)3 R 3m 3 2/m

II/D.09-50 Skippenite Bi2Se2(Te,S) R 3m 3 2/m

II/D.09-60 Tetradymite Bi2Te2S R 3m 3 2/m

II/D.09-70 Kawazulite Bi2(Te,Se,S)3 R 3m 3 2/m

Other Tetradymite Information

References:

NAME( Duda&Rejl90) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(AntBidBlaNic1)

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Tetradymite

Bi2Te2S
Dana No: 2.11.7.1 Strunz No: II/D.09-60
Locality:

Notes: