I’m calling this a turtle shell serpentine because the colors and banding remind me of a turtle shell.  The rich variety of colors in this rock can be clearly seen from the rough exterior even before cutting and polishing (see photos below).  Once cut and polished these colors pop even more showing a beautiful range of greens with the stark black stripe.

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.  They are formed by metamorphosis of oceanic basalt typically under high pressure and low temperature conditions.

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