Chalcopyrite and Siderite

Sample of coarse granular brass-yellow Chalcopyrite that is slightly iridescent. Chalcopyrite is entwined with curved rhombohedral subhedral Siderite that is light brown in colour and has a vitreous lustre. Average Siderite crystal size: 2.5 cm x 1.0 cm x 2.1 cm. Chalcopyrite (CuFeS2) can be brass-yellow or golden-yellow that is often tarnished iridescent or deep blue, purple and black. Lustre is metallic and streak is greenish black. Hardness is 3 1/2 to 4 and cleavage is poor in one direction. Chalcopyrite usually occurs as tetrahedral that typically have uneven crystal faces with striations in various directions. Chalcopyrite can also occur as massive, compact, granular or disseminated. Siderite (FeCO3) can be light to dark brown, reddish brown or white. Lustre is vitreous, pearly or dull. Streak is white or pale yellow and hardness is 3 1/2 to 4. Cleavage is perfect in three directions forming a rhombohedron. Siderite usually occurs as rhombohedral with curved faces but can also be prismatic, scalenohedral, granular, cleavable masses, compact, massive, botryoidal or fibrous in form.