Miedziankit z Miedzianki koło Chęcin

Abstract

MIEDZIANKITE FROM MIEDZIANKA NEAR CHĘCINY

Summary

Miedziankite found at Miedzianka near Chęciny, within the Świętokrzyskie Mountains, belongs to a group of sulphur salts, i.e. to the minerals which have regular symmetry and make an isomorphic rank tenantite-tetrahedrite. Goniometrical examinations of the miedziankite crystals allow to determine the merohedrism of faces {12l}, {131}, {123}, and consequently the presence of three twofold axes only. The faces (123), (123), (123), (123) make the right sphenoid. The values of spherical co-ordinates  j and r of the faces here considered do not differ from those characteristic of the regular system. Nevertheless, the symmetry of the miedziankite crystals may be considered orthorhombic.
X-ray examinations prove the presence of a superstructure observed in two directions, parallelly to the twofold axes. Dimensions of a characteristic cell of miedziankite are as follows: a = 10.24 A, b = 30.78 A, c = 40.92 A, space group – D¹₂, Z = 96.