Argyrodite

Ag8 GeS6
c 2001-2005 Mineral Data Publishing, version 1

Crystal Data: Orthorhombic, pseudocubic. Point Group: mm2. Pseudo-octahedra,dodecahedra, cubes, or as combinations of these forms, in crystals as large as 18 cm. Alsoradiating crystal aggregates, botryoidal crusts, or massive. Twinning: Pseudospinel law {111};
repeated interpenetration twins of pseudododecahedra on {111}.
Physical Properties: Fracture: Uneven to slightly conchoidal. Tenacity: Brittle.
Hardness = 2.5–3 VHN = n.d. D(meas.) = 6.29 D(calc.) = 6.32
Optical Properties: Opaque. Color: Steel-gray with a red tint, tarnishes black; inpolished section, gray-white with a violet tint. Streak: Gray-black. Luster: Strong metallic.
Pleochroism: Very weak. Anisotropism: Weak.
R1 –R2 : (400) 28.9–29.5, (420) 27.9–28.5, (440) 27.1–27.7, (460) 26.3–26.9, (480) 25.8–26.3, (500)25.3–25.8, (520) 25.0–25.4, (540) 24.7–25.2, (560) 24.6–25.0, (580) 24.5–24.9, (600) 24.4–24.9, (620)
24.5–24.8, (640) 24.6–24.9, (660) 24.5–24.9, (680) 24.6–25.0, (700) 24.7–25.0
Cell Data:

Space Group: P na21 . a = 15.149(1)b = 7.476(2)c = 10.589(1)Z=4X-ray Powder Pattern: Machacamarca, Bolivia.
3.02 (100), 1.863 (50), 2.66 (40), 3.14 (30), 2.44 (30), 2.03 (30), 1.784 (20)
Chemistry:
AgFe
GeSn
SbS

(1)
75.78
3.65
3.60
trace
16.92

(2)
74.20
0.68
4.99
3.36
trace
16.45

(3)
76.51
6.44

17.05

Total 99.95
99.68
100.00(1) Chocaya, Bolivia. (2) Aullagas, Bolivia. (3) Ag8 GeS6 .
Polymorphism & Series:

Forms a series with canfieldite.

Occurrence: In low-temperature polymetallic deposits with silver sulfosalts (Freiberg,Germany); in high-temperature Sn–Ag deposits (Bolivia).
Association: Canfieldite, stephanite, acanthite, pyrargyrite, polybasite, aramayoite, diaphorite,marcasite, pyrite, galena, sphalerite, cassiterite, siderite.
Distribution: In Germany, in Saxony, from the Himmelsfürst [TL] and other mines, Erbisdorf,
near Freiberg. In the Fournial mine, Massiac region, Cantal, France. At the Vale das Gatas
tungsten mine, near Vila Real, northern Portugal. From Silvermines, Co. Tipperary, Ireland. At anumber of localities in Bolivia, including Aullagas, Colquechaca, Potosı́, Oruro, Porco, Chocaya,and Machacamarca. At the Dolly Varden mine, Alice Arm, British Columbia, Canada. From Rico,Dolores Co., Colorado, USA. In the Wolyu mine, Youngdong district, South Korea. From Shuiji,Fujian Province, and in the Baiguoyuan deposit, Hubei Province, China.
Name:

From the Greek for silver-containing.

Type Material:

Mining Academy, Freiberg, Germany, 7058.

References: (1) Palache, C., H. Berman, and C. Frondel (1944) Dana’s system of mineralogy,(7th edition), v. I, 356–358. (2) Berry, L.G. and R.M. Thompson (1962) X-ray powder data forthe ore minerals. Geol. Soc. Amer. Mem. 85, 122. (3) Eulenberger, G. (1977) Die Kristallstruktur
der Tieftemperaturmodifikation von Ag8 GeS6 — Synthetischer Argyrodite. Monatshefte fürChem., 108, 901–913 (in German with English abs.). (4) Wang, N. (1978) New data for Ag8 SnS6(canfieldite) and Ag8 GeS6 (argyrodite). Neues Jahrb. Mineral., Monatsh., 269–272. (5) Criddle,A.J. and C.J. Stanley, Eds. (1993) Quantitative data file for ore minerals, 3rd ed. Chapman &Hall, London, 19.
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