The Black Hills and Mount Rushmore

We recently went to The Black Hills in South Dakota. Granite is really easy to find there. Granite has a high silica content and it's felsic in classification, meaning the magma was slow to cool and there is a high quartz content. It was very rough to the touch, indicating a phaneritic composition but, there were fine-grained areas, too, which is what the faces of Mount Rushmore are carved from. It was gray from far away but appeared speckled up close, which is classic granite coloring due to the presence of dark silicates.