Though I am not entirely sure if this is a true gneiss, the layered texture of this rock makes me think of a gneiss. Regardless it is very nice. From the coloring I believe it originated as oceanic basalt. There is a beautiful variety of greens, greys and blues within this rock along with accents of quartz.
Rock type: Gneiss, most likely from a basalt and quartz
This type of rock is referred to as a gneiss. The banding/layering occurs when a rock experience metamorphic temperatures and pressures and the minerals rearrange into layers as the rock is cooled.
Chemical composition: The exact composition is not known, however the rock contains quartz and metamorphosed oceanic basalt.