General Tetradymite Information
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Chemical Formula: |
Bi2Te2S |
Composition: |
Molecular Weight = 705.23 gm |
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Bismuth 59.27 % Bi |
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Tellurium 36.19 % Te |
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Sulfur 4.55 % S |
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______ |
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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 |
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ICSD 26720 |
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PDF 42-1447 |
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Tetradymite Image |
Images:
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Tetradymite Crystallography
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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 |
X Ray Diffraction: |
By Intensity(I/Io): 2.292(1), 3.1(1), 2.111(0.75), |
Forms:
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Forms:
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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]
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Physical Properties of Tetradymite
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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 |
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Optical Properties of Tetradymite
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RL Anisotrophism: |
Weak. |
RL Color: |
White. |
Reflectivity |
Standardized Intensity (100%) Reflection Spectra of Tetradymite in Air
| λ |
R1 |
R2 |
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∑ R1(λ) |
∑ R2(λ) |
| 400 nm |
50.00 |
52.70 |

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| 420 nm |
50.80 |
53.60 |

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| 440 nm |
51.60 |
54.50 |

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| 460 nm |
52.00 |
55.00 |

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| 480 nm |
52.40 |
55.40 |

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| 500 nm |
52.70 |
55.80 |

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| 520 nm |
53.00 |
56.20 |

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| 540 nm |
53.20 |
56.40 |

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| 560 nm |
53.30 |
56.50 |

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| 580 nm |
53.40 |
56.60 |

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| 600 nm |
53.50 |
56.70 |

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| 620 nm |
53.50 |
56.80 |

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| 640 nm |
53.40 |
56.90 |

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| 660 nm |
53.40 |
57.00 |

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| 680 nm |
53.40 |
57.10 |

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| 700 nm |
53.50 |
57.20 |

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Calculated Relative Intensity Colors of Tetradymite in Air
Relative Intensity |
0% |
20% |
40% |
60% |
80% |
100% |
120% |
140% |
160% |
170% |
| R1 |
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| R2 |
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Calculated Properties of Tetradymite
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Electron Density: |
relectron=6.19 gm/cc note: rTetradymite =7.63 gm/cc. |
Fermion Index |
Fermion Index = 0.02925 Boson Index = 0.97075 |
Photoelectric: |
PETetradymite =1,313.02 barns/electron U=PETetradymite x relectron=8,125.77 barns/cc. |
Radioactivity: |
GRapi = 0 (Gamma Ray American Petroleum Institute Units) Tetradymite is Not Radioactive |
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Tetradymite Classification
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Dana Class: |
2.11.7.1 (2)Sulfides - Including Selenides and Tellurides |
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(2.11)where Am Bn Xp, with (m+n):p=2:3 |
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(2.11.7)Tetradymite Group (Trigonal: R-3m) |
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2.11.7.1 Tetradymite Bi2Te2S R 3m 3 2/m |
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2.11.7.2 Tellurobismuthite Bi2Te3 R 3m 3 2/m |
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2.11.7.3 Tellurantimony Sb2Te3 R 3m 3 2/m |
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2.11.7.4 Paraguanajuatite Bi2(Se,S)3 R 3m 3 2/m |
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2.11.7.5 Kawazulite Bi2(Te,Se,S)3 R 3m 3 2/m |
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2.11.7.6 Skippenite Bi2Se2(Te,S) R 3m 3 2/m |
Strunz Class: |
II/D.09-60 II - Sulfides and sulphosalts |
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II/D - Sulfides with metal: sulfur, selenium and tellurium < 1:1, Tellurides with Copper, Silver, Gold |
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II/D.09 - Tetradymite group, Tellurantimony - Kawazulite series |
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II/D.09-10 Tellurantimony Sb2Te3 R 3m 3 2/m |
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II/D.09-20 Tellurobismuthite Bi2Te3 R 3m 3 2/m |
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II/D.09-30 Paraguanajuatite Bi2(Se,S)3 R 3m 3 2/m |
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II/D.09-50 Skippenite Bi2Se2(Te,S) R 3m 3 2/m |
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II/D.09-60 Tetradymite Bi2Te2S R 3m 3 2/m |
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II/D.09-70 Kawazulite Bi2(Te,Se,S)3 R 3m 3 2/m |
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Other Tetradymite Information
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References: |
NAME( Duda&Rejl90) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(AntBidBlaNic1) |
See Also: |
Links to other databases for Tetradymite :
1 -Am. Min. Crystal Structure Database
2 -Athena
3 - Crocoite.com Mineral Locations
4 - EUROmin Project
5 -Google Images
6 -Google Scholar
7 -Handbook of Mineralogy (UofA)
8 -MinDAT
9 -MinMax(Deutsch)
10 -MinMax(English)
11 -Mineralienatlas (Deutsch)
12 -QUT Mineral Atlas
13 - Scandinavian mineral gallery
14 - WWW-MINCRYST
15 -École des Mines de Paris
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Print or Cut-and-Paste your Tetradymite Specimen Label here :
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Tetradymite
Bi2Te2S
Dana No: 2.11.7.1 Strunz No: II/D.09-60
Locality:
Notes:
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