Franckeite

Pb21.7Sn9.3Fe4.0Sb8.1S56.9

Crystal Data: Triclinic. Point Group: 1 . Crystals, tabular on {010}; elongated along [100], to6 cm, striated on {010}, may be warped or bent; typically, in spherical, rosette or cauliflowerlike
aggregates of thin plates; commonly massive, radiated, or foliated. Twinning: Complex twinningwith [010] as a twin axis.
Physical Properties: Cleavage: {010}, perfect. Tenacity: Flexible, inelastic; slightly malleable.
Hardness = 2.5-3 VHN = n.d. D(meas.) = n.d. D(calc.) = 8.98
Optical Properties: Opaque. Color: Grayish black. Streak: Grayish black. Luster: Metallic.
Anisotropism: Weak.
R1-R2: (400) 38.2-39.4, (420) 37.9-39.2, (440) 37.6-39.0, (460) 37.3-38.7, (480) 36.9-38.5,(500) 36.6-38.2, (520) 36.2-37.9, (540) 35.8-37.6, (560) 35.4-37.3, (580) 35.0-36.9, (600) 34.6-36.5,(620) 34.2-36.1, (640) 33.8-35.7, (660) 33.4-35.3, (680) 33.0-34.9, (700) 32.6-34.5
Cell Data: Superspace Group: C 1 . Z = 2 Pseudohexagonal H layers (MS2, M = Sn4+, Fe2+);
a = 3.665(8) b = 6.2575(16) c = 17.419(5) α = 95.25(2)° β = 95.45(2)° γ = 89.97(2)°.
Pseudotetragonal Q slabs (MS, M = Pb2+, Sn2+, Sb3+); a = 5.805(8) b = 5.856(16) c = 17.338(5).
X-ray Powder Pattern: Bolivia.
3.44 (100), 2.91 (100), 2.86 (100), 2.82 (100), 2.05 (75), 4.30 (50), 3.11 (50)
Chemistry:PbFeZnAgCu(1)
50.57
2.48
1.22(2)
46.23
2.69
0.57
0.97(3)
50.14
2.60
0.77
0.02

SnSbS
rem.
Total

(1)
(2)
(3)
12.34 17.05 13.06
10.51 11.56 12.45
21.04 21.12 21.49
0.71.
98.87 100.19 100.53(1) Chocaya, Bolivia. (2) Poopó, Bolivia. (3) San Jose, Bolivia; electron microprobe analysis;corresponds to Pb20.54Ag0.60Cu0.03Sn9.34Fe3.95Sb8.68S56.87.
Mineral Group: Cylindrite-franckeite family.
Occurrence: In hydrothermal Ag-Sn deposits (Bolivia); in a limestone contact metamorphic deposit(Kalkar quarry, California, USA).
Association: Cylindrite, teallite, plagionite, zinkenite, cassiterite, wurtzite, pyrrhotite, marcasite,arsenopyrite, galena, pyrite, sphalerite, siderite (Bolivia); cassiterite, galena, stannite, teallite,cylindrite (Russia).
Distribution: In Bolivia, from Chocaya [TL], Poopó, Oruro, Llallagua, Huanuni, Colquechaca, andCerro Rico, Potosí. At the Pirquitas mine, Jujuy Province, Argentina. In the Thompson mine,
Darwin district, Inyo Co., and the Kalkar quarry, Santa Cruz, Santa Cruz Co., California, USA.
From near the headwaters of the east branch of the Coal River, Yukon Territory, Canada. At Vens
Haut, Cantal, France. In the Sinantscha zinc deposit, Sichota-Alin, and from Smirnowsk,Transbaikalia, Russia. At the Changpo-Tongkeng tin deposit, Dachang district, Guangxi
Autonomous Region, China. From the Hoei tin mine, Oita Prefecture, Japan. At the Renison Bellmine, Tasmania, and the Wallah Wallah mine, Rye Park, New South Wales, Australia.
Name: Honors the mining engineers Carl and Ernest Francke.
References: (1) Palache, C., H. Berman, and C. Frondel (1944) Dana’s system of mineralogy, (7thedition), v. I, 448-450. (2) Moh, G. (1987) Mutual Pb2+/Sn2+ substitution in sulfosalts. Mineral.
Petrol., 36, 191-204. (3) Williams, T.B. and B.G. Hyde (1988) Electron microscopy of cylindrite andfranckeite. Phys. Chem. Minerals, 15, 521-544. (4) Wang, S. and K.H. Kuo (1991) Crystal lattices
and crystal chemistry of cylindrite and franckeite. Acta Cryst., A47, 381-392. (5) Criddle, A.J. andC.J. Stanley, Eds. (1993) Quantitative data file for ore minerals, 3rd ed. Chapman & Hall, London,175. (6) Makovicky, E., V. Petříček, M. Dušek, and D. Topa (2011) The crystal structure offranckeite, Pb21.7Sn9.3Fe4.0Sb8.1S56.9. Amer. Mineral., 96, 1686-1702.
Mineralogical Society of America

Handbook of Mineralogy

Revised 5/1/2021