Pyrite - FeS2
Pyrite is a metallic looking compound, which has a somewhat golden luster, although real gold is much more yellow. Pyrite can form beautiful shiny crystals. These crystals frequently are cubic and the picture above shows two nearly perfect cubic crystals. A video is made as well, showing how shiny these crystals in reality are. The motion of the video makes it possible to see the shiny properties.
Pyrite also can be in the form of irregularly shaped clumps. These clumps also have a golden luster and look metallic, but they are not as shiny as the big crystals, shown above.