cubanite

Cubanite is a rare copper iron sulfide mineral with the chemical formula CuFe2S3. It crystallizes in the orthorhombic system and typically occurs as granular or massive aggregates, though prismatic crystals have been found. The mineral is known for its distinctive metallic luster and brass-yellow to bronze color. It is often found in association with other sulfide minerals such as chalcopyrite and pyrrhotite, and it is considered a secondary mineral, often forming through the alteration of other copper-bearing minerals.

Cubanite is relatively soft, with a Mohs hardness of 3.5 to 4, and has a specific gravity of around 4.0. Its streak is dark gray to black. The mineral was first described in 1914 from samples found in the La Maya mine in Cuba, which is where it derives its name. While not an economically important ore mineral, cubanite is of interest to mineral collectors and geologists studying hydrothermal ore deposits. It can also be found in metamorphosed sedimentary rocks and some mafic and ultramafic intrusions. Its formation is often linked to higher temperatures and specific sulfur fugacity conditions.