The interactions of synthetic chalcocite surfaces with diethyldithiophosphate, potassium salt, K[S2P-(OC2H5)(2)], were studied by means of P-31 cross-polarization/magic angle spinning (CP/MAS) NMR spectroscopy and scanning electron microscopy (SEM). To identify the species formed on the Cu2S surfaces, a polycrystalline {Cu-6(I)[S2P(OC2H5)(2)](6)} cluster was synthesized and analyzed by SEM, powder X-ray diffraction techniques and solid-state P-31 CP/MAS NMR and static Cu-65 NMR spectroscopy. P-31 chemical shift anisotropy (CSA) parameters, &UDelta;(CS) and η(CS), were estimated and used for assigning the bridging type of diethyldithiophosphate ligands in the {Cu-6(I)[S2P(OC2H5)(2)](6)} cluster. The latter data were compared to P-31 CSA parameters estimated from the spinning sideband patterns in P-31 NMR spectra of the collector-treated mineral surfaces: formation of polycrystalline {Cu-6(I)[S2P(OC2H5)(2)](6)} on the Cu2S surfaces is suggested. The second-order quadrupolar line shape of Cu-65 was simulated, and the NMR interaction parameters, C-Q and η(Q), for the copper(I) diethyldithiophosphate cluster were obtained.