The crystal structure of eclarite, first determined by Kupcik in 1984, has been refined on material from the scheelite deposit at Felbertal, Salzburg Province, Austria, to an R 1 value of 4.5% on the basis of 4141 unique reflections [ F o > 4σ( F o )]. The chemical formula of material examined, based on 20.85 large cations (Z = 4) is Cu 0.76 Fe 0.45 Ag 0.12 Pb 8.14 Bi 12.59 S 27.91 ; its unit-cell parameters are a 4.0307(1), b 22.7011(6), and c 54.615(1) A, space group Pmcn . All the principal features of Kupcik’s structure were confirmed. Three cation sites appear split into Pb and Bi subsites, and the octahedral site of the “cosalite-like” fragment is a partially occupied Bi site, flanked by three-fold coordinated, partly occupied Cu1 and Cu2 sites. The tetrahedral (Cu,Fe) site is split into a triangular position and a tetrahedral position. Replacement of Fe by Cu at the tetrahedral site and replacement of Bi by Cu at the octahedral site are positively correlated. They result in a general formula of eclarite equal to Cu 1.5 n Fe 1− n Pb 9–1.25 n Bi 12+ n S 28 in which n is the molar proportion of the copper-based fully substituted ideal end-member Cu 1.5 Pb 7.75 Bi 13.0 S 28 , and (1– n ), that of the Fe-based ideal end-member FePb 9 Bi 12 S 28 . We propose a new interpretation of the crystal structure of eclarite, as a patchwork of large galenobismutite-like regions joined by interstitial elements.