Most of the rocks exposed along the length of the Black Canyon are Precambrian in age (older than 500 million years) and are either metamorphic, or igneous, with some sedimentary layers evident along the North Rim. The rocks in the Black Canyon have a wide variety of minerals. Here is a brief look at some of them and where they may be found.
Rock is usually buried deep within the Earth's crust (six to eight miles, for instance) before temperatures and pressures are high enough to melt and change their physical and chemical composition. Black Canyon's metamorphic rocks have been altered to the point that little trace of the original rock remains. However, geologists suspect that the original rocks, or protoliths were sands, mud and volcanic debris that accumulated on the floor of an ancient sea. The time of metamorphism is estimated at 1.7 to 1.9 billion years ago. Gneiss and schist are examples of metamorphic rocks found in the Black Canyon. These rocks blend from one to another because of variations in the heat and pressure which occurred when some rocks were buried deeper than others.
PLEASE REMEMBER... Collecting rock specimens in Black Canyon of the Gunnison National Park is illegal.
One of the most famous examples of the quartz monzonite is the Curecanti Needle (along Morrow Point Reservoir). The monzonite is harder than the metamorphic rocks and weathers more slowly. The needle was created when the waters of the Gunnison River and Blue Creek carved away the surrounding metamorphic rock, leaving the Needle in their wake. The third side is separated by weathering of a fault system. More information »
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The Interior of the Earth