I am calling this a lightning serpentine because the pattern of the white minerals cutting through this piece remind me of lightning.  I am fairly certain the main component of this rock is serpentine.  The piece was cut from a rock found along Deer Creek in Washington State.

Rock type: Serpentine

The name serpentine can refer to a specific type of rock, however I have found that it is also used for a catch all name for many metamorphic green rocks.  Serpentines are ultramafic metamorphic rocks and contain a wide range of rich green colors.

Chemical composition: Serpentine minerals typically have a general chemical formula of (Mg,Fe)3Si2O5(OH)4