Basement Complex of the Rockies
The majority of the rocks found in the basement complex are highly metamorphosed igneous and sedimentary rock dating back between 3-4 billion years old.
Granitic Gneiss
Gneiss is a metamorphic rock that has a banded light and dark striations. The light bands are potassium feldspars and the dark bands are plagioclase feldspars. Much of the gneiss in the area contained porphoroblasts of garnets, which you can see in the image above.
Basement Complex Rocks
Granite
Granite is one of the major igneous rocks that is found in the basement complex. It is high in quartz and has biotite as the dark specs within the body. Epidote shows up in small quantities but is easily eroded. Many of the granite bodies were formed by dikes and lava flows over the past 4 billion years.
Schist
This type of rock is of the same composition of the gneiss mentioned before, but the difference is the grade of metamorphism imposed on these rocks. The striations in the gneiss are much less visible here and the rocks begin to take an apperance of something other than the sedimentary rock that was originally deposited.
