Franckeite Mineral Data

Franckeite Mineral Data +

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General Franckeite Information

Chemical Formula:

(Pb,Sn)6Fe++Sn2Sb2S14

Composition:

Molecular Weight = 1,995.14 gm

Iron 2.80 % Fe

Tin 13.68 % Sn

Antimony 12.20 % Sb

Lead 48.81 % Pb

Sulfur 22.50 % S

______

100.00 %

Empirical Formula:

Pb_4.7Sn_2.3Fe²⁺Sb₂S₁₄

Environment:

Hydrothermal Ag-Sn deposits and limestone contact metamorphic deposit.

IMA Status:

Valid Species (Pre-IMA) 1893

Locality:

Found in Bolivia at Poopo in Oruro and at Las Aminas, southeast of Chocaya, in Potosi. Link to MinDat.org Location Data.

Name Origin:

Named after the mining engineers, Carl and Ernest Francke.

Franckeite Image

Images:

Franckeite

Comments: Massive franckeite with pockets of small .5 mm crystals.
Location: Animas Mine, Atocha-Quechisla district, Sud Chichas Province, Potos? Department, Bolivia. Scale: 25x20x15 mm.
© John Betts - Fine Minerals

Images:

Franckeite Potosiite

Comments: Visually indistinguishable metallic potosiite/franckeite crystals to 6 mm..
Location: San Jose mine, Oruro City, Oruro Department, Bolivia. Scale: Crystal size 6 mm.
© Rob Lavinsky

Franckeite Crystallography

Axial Ratios:

a:b:c =8.0584:1:2.9725

Cell Dimensions:

a = 46.9, b = 5.82, c = 17.3, Z = 8; alpha = 90°, beta = 94.68°, gamma = 90° V = 4,706.43 Den(Calc)= 5.63

Crystal System:

Triclinic - PinacoidalH-M Symbol ( 1) Space Group: P1

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

By Intensity(I/I_o): 2.82(1), 3.44(1), 2.91(1),2.86(1), 2.05(0.75), 3.11(0.5), 4.3(0.5),

Forms:

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

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Physical Properties of Franckeite

Cleavage:

[001] Perfect

Color:

Grayish black, Blackish gray.

Density:

5.5 - 5.9, Average = 5.7

Diaphaniety:

Opaque

Fracture:

Flexible - Flexible fragments.

Habit:

Massive - Fibrous - Distinctly fibrous fine-grained forms.

Habit:

Radial - Crystals radiate from a center without producing stellar forms (e.g. stibnite)

Habit:

Tabular - Form dimensions are thin in one direction.

Hardness:

2.5 - Finger Nail

Luster:

Metallic

Streak:

grayish black

Optical Properties of Franckeite

RL Anisotrophism:

Weak.

Reflectivity

**Standardized Intensity (100%) Reflection Spectra of Franckeite in Air**
λ	R₁	R₂	∑ R₁(λ)	∑ R₂(λ)
400 nm	40.90	42.00
420 nm	40.20	41.40
440 nm	39.50	40.80
460 nm	38.80	40.20
480 nm	38.20	39.70
500 nm	37.60	39.10
520 nm	37.00	38.60
540 nm	36.40	38.20
560 nm	35.80	37.70
580 nm	35.30	37.30
600 nm	34.80	36.80
620 nm	34.40	36.50
640 nm	33.90	36.00
660 nm	33.50	35.70
680 nm	33.10	35.40
700 nm	32.80	35.10

**Calculated Relative Intensity Colors of Franckeite in Air**
Relative Intensity	0%	30%	60%	90%	100%	120%	150%	180%	210%	240%	260%
R₁
R₂

Calculated Properties of Franckeite

Electron Density:

r_electron=4.81 gm/cc
note: r_Franckeite=5.63 gm/cc.

Fermion Index

Fermion Index = 0.13289
Boson Index = 0.86711

Photoelectric:

PE_Franckeite= 965.32 barns/electron
U=PE_Franckeite x r_electron=4,643.85 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Franckeite is Not Radioactive

Franckeite Classification

Dana Class:

3.1.4.2 (3)Sulfides - Sulfosalts

(3.1)where z/y > 4 - (A+)i (A++)j [By Cz], A=metals, B=semi-metals, C=non-metals

(3.1.4)Dana Group

3.1.4.1 Cylindrite Pb3Sn4FeSb2S14 P1 1

3.1.4.2 Franckeite (Pb,Sn)6FeSn2Sb2S14 P1 1

3.1.4.3 Incaite Pb4Sn4FeSb2S15 P1 ? 1

3.1.4.4 Potosiite Pb6Sn2FeSb2S14 P 1 ? 1

Strunz Class:

II/C.17-70 II - Sulfides and sulphosalts

II/C - Sulfides with metal: sulfur, selenium and tellurium = 1:1

II/C.17 - Hertzenbergite - Kylindrite series

II/C.17-10 Herzenbergite SnS Pbnm 2/m 2/m 2/m

II/C.17-20 Stistaite SnSb R 3m 3 2/m

II/C.17-30 Mohite Cu2SnS3 P1 1

II/C.17-40 Teallite PbSnS2 Pbnm 2/m 2/m 2/m

II/C.17-45 Suredaite! PbSnS3 P nma 2/m 2/m 2/m

II/C.17-50 Potosiite Pb6Sn2FeSb2S14 P 1 ? 1

II/C.17-55 Levyclaudite Pb8Sn7Cu3(Bi,Sb)3S28 A2 ? 2

II/C.17-60 Incaite Pb4Sn4FeSb2S15 P1 ? 1

II/C.17-70 Franckeite (Pb,Sn)6FeSn2Sb2S14 P1 1

II/C.17-80 Cylindrite Pb3Sn4FeSb2S14 P1 1

Other Franckeite Information

References:

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

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Franckeite

(Pb,Sn)6Fe++Sn2Sb2S14
Dana No: 3.1.4.2 Strunz No: II/C.17-70
Locality:

Notes: