Analyses of 191 samples of the tennantite-tetrahedrite series from different associations of minerals in the mineral deposit in Permian rocks of the Western Carpathians by EMA method show in formula unit variability if Cu¹⁺ from 9.5 to 11.6 atoms, total Me²⁺ (Fe + Zn + Hg) from 0.3 to 2.8 atoms, Me¹⁺ + Me²⁺ from 9.5 to 12.3 atoms, complete substitution of As and Sb (Me³⁺ from 3.5 to 4.3 atoms) and from 12.4 to 13.4 atoms of S. The contents of Ag, Pb, Bi, Te and Se are increased by up to 2.4 atomic % in the same type of deposits. The variability of the physical properties of the tennantite-tetrahedrite series reflects different chemical compositions: unit cell (a₀) from 1.0204 to 1.0369 nm, microhardness (VHN_50g) from 275 to 361, reflectivity (R_546nm) from 26.7 to 31.2 %.