This is the mineral Pyrite. It has a striking brass and yellow metallic luster but produces a brown or greenish black streak when drawn across a white ceramic streak plate. It’s a relatively dense mineral, with a specific gravity of about 5, thus making it feel heavy in your hand. It ranks between 6 and 6.5 on Mohs hardness scale. Pyrite can be scratched by Quartz, which ranks 7, but not by Apatite, which ranks 5. In unconfined spaces, Pyrite crystals grow as well-defined cubes, leading some to hypothesize that the mineral would exhibit cubic cleavage. This is not the case, however, as Pyrite yields indistinct or no cleavage. When broken, it occasionally fractures in a conchoidal pattern, which resembles the smooth and concave undulations of a seashell. Pyrite contains only 2 elements, Iron and Sulfur, and has the chemical formula FeS2. It thus belongs to the Sulfide chemical family. Sulfides are minerals consisting of Sulfur and one or more metals. Pyrite is commonly known as Fool’s Gold due to its yellow color and metallic luster. There is no Gold in Pyrite, however. Recall that its two elements are Iron and Sulfur, both of which are very common in Earth’s crust. The Iron in Pyrite can spark if the mineral is struck against metal or some other hard surface, making it useful for starting fires. Its name, in fact, is derived from the Greek word pyr, which means fire.