Rib Mountain Quartzite - Wausau, WI - Places of Geologic Significance on Waymarking.com

From the Rib Mountain State Park informational sign:
"This park is located on the summit of Rib Mountain, one of the most prominent isolated hills in Wisconsin. Just as the stump covered field enables us to picture the forest that has long since been cut - so by study of the old worn down stumps of mountains, the geologist is able to picture the mountains that once covered all of Wisconsin. During countless ages these mountains were gradually worn down to a plain. In a few places a harder ridge or peak called a monadnock still rises considerably higher than the general level of the plain. Rib Mountain, the highest rock hill in the state, is such a monadnock rising to a height of 1940 feet above the sea and nearly 800 feet above the Wisconsin River.

The rock was originally a sandstone that has been thoroughly cemented to form a hard glass like rock called quartzite. Ripple marked slabs indicate that the original constituents were loose sand washed by waves. The original sandstone bedding was horizontal. Later folding resulted in the present nearly vertical position of the quartzite beds. Rib Mountain is a Monadnock which owes its superior elevation to the fact that it is composed of Quartzite and has therefore suffered less erosion than the granite which surrounds it. The Quartzite crags and the talus slopes indicate that the park was not glaciated.

From the Quartzite informational sign:
"The dense hard rock forming rib mountain is called quartzite. It was originally loose sand but was changed first to sandstone by cementing of the sand grains and then to quartzite by earth movements and fluids which compressed and hardened the rock."