The Blue Hills rise about 600 feet above the landscape of northwestern Rusk, southwestern Sawyer, and northeastern Barron Counties. The hills are composed of erosion-resistant red quartzite that is topped with a thin layer of glacial deposits. This quartzite, consisting of metamorphosed river and near-shore ocean sediment—mainly sand—deposited approximately 1.7 billion years ago, is similar in age and appearance to the quartzite that forms the Baraboo Hills and several other prominent uplands in central Wisconsin, Minnesota, and South Dakota. Some of these quartzite localities contain beds of catlinite (also called pipestone), a soft rock that is still quarried and carved into pipes and effigies by Native Americans.