The nickel ternary chalcogenides are a class of chemical compounds that contain nickel, one other metallic element, and a chalcogenide. Nickel combined with another metal and oxygen forms a series of double nickel oxides which are referred to as "nickelates" or, more precisely, "oxonickelates". This page lists the many other well-defined double compounds of nickel with sulfur, selenium and tellurium; double nickel oxides are listed elsewhere.