Commonly known as Fool's gold for obvious reasons, it's really comprised of Iron Sulphide, Fe2S, and is rather common. But it can form amazingly perfect Cubic Crystals that look as if they have been machined, and these can fetch good prices.
Marcasite is another form of Pyrites often used in Jewellery.
Pyrites carries a Solar energy. It is expansive and intuitive, yet being cubic also has a very grounded materialistic edge. Extremely good at channeling creative energy in a practical manner.
Iron Pyrites is also very protective. When worn it shields the Heart from negative and draining energies.