The octahedron shape is one of the five Platonic shapes and is third in sacred geometry.  The shape has eight triangles with six vertices, eight faces and twelve edges.  This unique shape does occur in nature with several gemstones such as diamonds, fluorite, magnetite, spinel, etc.  The octahedron represents the Air Element which allows you to be able to clear blockages in your life and to overcome difficulties.  It also supports you in meditation and the path of levitation as it creates an atmosphere conducive to counter-gravity.  The shape of the octahedron promotes wellness and encourages you to find within yourself the capacity for forgiveness (of self & others) and promotes thought processes of acceptance and understanding.  Because it is a gemstone that is double terminated and features six vertices it does wonders for amplification work; especially with healing.