Yarrowite – Cu₉S₈ – is one of the forms of copper sulfide. It is relatively rare and is part of copper ores.

There are nine different minerals that are formed only by Cu+S. Copper sulfide formed at low temperatures (T<~105ºC) is monoclinic chalcocite. At high temperatures (T>~105ºC) (including in blast furnaces) digenite (Cu9S5 trigonal) is formed. Another copper sulfide, djurleite (Cu31S16 monoclinic), is easily confused with chalcocite. Other copper sulfides are anilite (Cu7S4 orthorhombic), roxbyite (Cu9S5 monoclinic), spionkopite (Cu39S28 trigonal), yarrowite (Cu9S8 trigonal), geerite (Cu8S5 trigonal) and covellite (CuS hexagonal).

In several of these minerals, there are substitutions of Cu by varying amounts of Ag, Fe, and Mn, as well as substitutions of S by Se and Te. Crystals with digenite x chalcocite and digenite x covellite mixtures occur, and there are serious sample preparation problems. This set of complications has historically caused much confusion and identification errors.