Semseyit a fizélyit z polymetalického ložiska Bohutín u Příbrami, Česká republika

Pages 11-16
Bulletin mineralogicko-petrologického oddělení Národního muzea v Praze | 2008/16/1

At mine dump of mine Štefánik, the ore deposit Bohutín near Příbram, central Bohemia, Czech Republic, rich aggregates of semseyite crystals with inclusions of fizelyite and galena were found. Semseyite forms steel grey tabular crystals up to 1.5 mm in length with considerable metallic luster growing to rich aggregates in the cavities of quartz - sphalerite - calcite ore gangue. In reflected light it is sligthly yellowish grey with distinct bireflectance (bluish green - grey) and anisotropic with rotation tints in shades of greyish blue to greyish brown. It has a mean VHN (20 g load) of 195 (177-211) kp/mm2 with KVH 1.15. Semseyite is monoclinic, space group C21/c, the unit-cell parameters refined from X-ray powder data are: a 13.643(5), b 11.972(3), c 24.607(8) Å, β 106.24(4)o, V 3859(2) Å3. Chemical analyses (mean of 9 points) yielded the average composition Ag 0.03, Pb 52.18, Sb 27.85, Bi 0.02, As 0.05, S 19.36, total 99.50 wt. %, corresponding to (Pb8.82Ag0.01)Σ8.83(Sb8.01As0.02)Σ8.03S21.14 on the basis of 38 apfu. Fizélyite forms abundant inclusions up to 45 x 8 μm in size in semseyite aggregates. The average results of chemical analyses (mean of 5 points) are: Ag 7.79, Fe 0.10, Pb 38.20, Cd 0.27, Cu 0.03, Sb 33.04, Bi 0.01, As 0.06, S 20.32, total 99.82 wt. % corresponding to (Pb13.90Cd0.18Fe0.14)Σ14.22(Ag5.44Cu0.03)Σ5.47(Sb20.46As0.06Bi0.01)Σ20.53S47.78 on the basis of 88 apfu. The calculated values Nchem = 4.34 (4.27 - 4.42) and %And = 62.06 (61.52 - 63.16) are given. Chemical compositions of both studied sulfosalts are compared with published data. The succession of origin of minerals in the studied samples is as follows: quartz IV → galena II → sphalerite IV → semseyite → fizélyite → calcite II.

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