Pyrite: Difference between revisions

Pyrite may form into many different shapes such as cubes, octahedrons, and pyritohedrons.  Pyrite's shape is determined by many different factors.  These factors are temperature, pressure, and what type of rock it is formed in.  If the temperature is around 250^oC then the crystal that is formed will be needle-like. During the increase in temperature to about 450^oC, the pyrite will take shape into first a cube, then an octehedron, then finally at the highest temperature the shape of the pyrite will be a pyritohedron, which is a twelve faced structure each face being pentagonal.  Sometimes during the formation of pyrite the temperature will change very often, this change in temperature can cause the formation of the pyrite to change. This will ultimately cause the pyrite to look like a mix of two different shapes, either cube-octahedrons and octahedral-pyritohedrons.  The constant change in temperature also leaves lines on the faces of the pyrite, because of this continual change from forming one shape to forming another.  When multiple cubic pyrite are forming, they often create penetrating twins which happens when two of the cubic pyrite grow into or out of each other.  Pyrite can also form into many other various structures such as radiating, grainy, flaky, mammilary, encrusting, nodular, and fibrous crystals.  Also they can form as flattened disks, given the name "pyrite suns". <ref name=foolsgold/>