Acta Musei Moraviae

New knowledges on sulfosalt mineralization of the deposit Hůrky, Čistá-Jesenice Massif (Czech Republic)

New samples of hydrothermal sulfosalt mineralization were recently collected at the mine dump of the vein No. 1 of the abandoned small deposit Hůrky near Velká Chmelištná in the Čistá-Jesenice Massif, 14 km WSW of Rakovník, Central Bohemia Region, Czech Republic. Beside pyrite and sphalerite, galena and sulfosalts form grey to dark grey aggregates and crystals up to several mm in size, which are enclosed in quartz gangue. Gustavite forms abundant subhedral to euhedral elongated grains up to 100 μm in length in galena. It is usually associated with felbertalite, heyrovskýite and vikingite. The calculated value of N_chem for gustavite is ranging from 3.97 to 4.17 and the L% of lillianite substitution varies between 6.2–89.7. Minor contents of Cd (up to 0.04 apfu) and Te (up to 0.02 apfu) are interesting. Abundant vikingite occurs as subhedral to euhedral elongated crystals up to 400 μm in length in galena, in association with heyrovskýite, gustavite and felbertalite. Vikingite from Hůrky has calculated value of N_chem in the range 5.12–5.66 and 42.5–55.5 L% of lillianite substitution. Minor concentrations of Cd (up to 0.18 apfu) and Te (up to 0.10 apfu) were detected. The average (n=30) empirical formula of vikingite based on S+Te = 30 apfu is (Ag_3.40Cu_0.07)Σ_3.47(Pb_10.60Cd_0.11)_Σ10.71Bi_11.38(S_29.92Te_0.08)_Σ30.00. Heyrovskýite forms abundant anhedral to euhedral grains up to 0.5 mm in size in galena and intergrowths with felbertalite, gustavite and vikingite. The calculated value of N_chem for new samples of heyrovskýite from Hůrky varies from 6.55 to 7.32. The observed lillianite substitution in the range 29.9–47.8 L% is significantly higher than was found in the type material of heyrovskýite from this locality with values ranging from 8 to 19 L%. Rare felbertalite occurs as subhedral to euhedral elongated grains up to 150 μm in length in galena, usually in association with heyrovskýite, vikingite and gustavite. The Ag and Cu contents in felbertalite are 0.51–0.72 and 1.80–2.01 apfu, respectively, and minor concentrations of Cd (up to 0.06 apfu) and Te (up to 0.09 apfu) were also detected. The average (n=22) empirical formula of felbertalite based on sum of all atoms = 35 apfu is Cu_1.94Ag_0.59(Pb_4.81Cd_0.03)_Σ4.84(S_19.14Te_0.08)_Σ19.22. Very rare cosalite occurs as grains up to 30 × 80 μm in size lined by felbertalite in galena aggregates. The Ag and Cu contents in cosalite are 0.91–1.16 and 1.49–1.62 apfu, respectively, and minor concentrations of Te (up to 0.09 apfu) and In (up to 0.02 apfu) were also detected. The average (n=19) empirical formula of cosalite based on S+Te = 20 apfu is Cu_1.58Ag_1.03(Pb_7.34In_0.01)_Σ7.35Bi_7.43(S_19.92Te_0.08)_Σ20.00.