Tenorite is a blackish-colored copper oxide mineral (CuO). It usually forms coatings resulting from oxidation of native copper (Cu) or copper-bearing sulfide minerals. The typical weathering/alteration sequence of exposed native copper is: cuprite to tenorite to malachite. Tenorite typically is nonmetallic black to metallic dark gray in appearance, and is moderately soft (H = 3.5 to 4).
Tenorite (black) mixed with chrysocolla (blue) in copper ore (4.0 cm across) from the Algomah Mine of northern Michigan. Tenorite and chrysocolla are the major copper ore minerals at this mine.