This rock was found on a Washington beach, though I’m not sure of its actual origin.  Each face of the cube shows off the beautiful, large mineral grains that are characteristic of pegmatites.  Each of these minerals creates a mosaic of colors and shapes that captures the imagination and beauty seen through such rocks.

Rock type: Pegmatite

Pegmatites are large grained plutonic rocks.   They form when magma is slowly cooled underground which allows the mineral grains to grow.  This cooling process can take hundreds of millions of years and results in amazing mixtures of large crystals.  This sample is dominated by quartz (white), potassium feldspar (pink) and biotite mica (black).

Chemical composition:  Biotite (K(Mg,Fe)3AlSi3O10(F,OH)2 -approximate composition), Potassium feldspar (most likely orthoclase KAlSi3O8) and quartz (SiO2).