Abstract:
Parageorgbokiite, p-Cu502(Se03)2Cl2, was found in the 2nd cinder cone of the great fissure Tolbachik eruption (Kamchatka peninsula, Russia). The mineral occurs in association with ralstonitc, tolbachitc, melanothallite, chalcocyanitc, euchlorine, Fe oxides, tenorite, native gold, sophiitc, sulfates of Na, Ca, Mg, and some other copper sclcnitcs. Its formation temperature may be estimated as 400-625° C. Mineral has a green color, light-grccn streak, and vitreous luster. Brittle, Mohs' hardness 3-4. Cleavage none observed. Density (calculated) 4.70 g/cm3. Biaxial, optically poisitive. a = 2.05(1), p =2.05(1), у = 2.08(1), 2Kmcas ~ 0°, 2УЫс = 0(5)°. Optic orientation: X= a, other details unclear. Pleochroism: X, Y- grass-green, Z- yellowish-green. Empirical formula calculated on the base of О + CI = 10 is as following: Cu49|Pb002Oi 8б(5еОз)2С12 м; simplified formula: Cu502(Se03)2Cl2. Monoclinic, P2i/c, a = 5.3982(5), b = 8.0543(8), с = 11.128(1) A, P = 99.258(2)°, V= 477.53(8) A3, Z= 2. The mineral belongs to a new structural type of inorganic compounds. Its name points out its dimorphism with gcorgbokiite, the mineral named in honor of G. B. Bokii, the prominent Russian crystal chemist (1909-2000).
