As magma cools and solidifies, water becomes concentrated, making the remaining magma more fluid. That last bit of magma to cool moves easily into the cracks in the surrounding rock before cooling and forming a type of granite called Pegmatite. The light colored streaks at Painted Wall in Black Canyon of the Gunnison National Park are an impressive example of this phenomenon. For reference, those are full size trees above the rim of the canyon. At 2,250 feet high, Painted Wall is Colorado’s tallest cliff.
The patterns in the rock look great in black & white too.
Check back Tuesday for the long overdue Part 2 of my Colorado Fall Color Trip Report.