City of Minneapolis - 218 North Rock Minneapolis, KS 67467 - 785-392-2176
The rocks at Rock City are huge sandstone concretions.
In an area about the size of two football fields, 200 rocks--some as large as houses--dot the landscape. There is no other place in the world where there are so many concretions of such giant size.
Owned by a local non-profit corporation, the site is operated as a public park. Open 9AM to 5 PM daily, May 1 to September 1. Admission is $3. /adult and $. 50/child.
Geologists are in general agreement that these concretions were formed millions of years ago of Dakota Sandstone, which was deposited when areas of Kansas were covered by an inland sea.
At one time, the surface of the land was higher than it is now, and the rock occupying this space was a sandstone where individual grains of sand were poorly cemented together. Underground waters containing dissolved calcium carbonate circulated through the porous rock with ease and in doing so deposited calcium carbonate in the open spaces between the sand grains, thereby cementing them together. Instead of proceeding evenly, the precipitation of this natural cement began at a number of scattered points where, perhaps, there was a fossil or an extra large grain of sand to serve as a nucleus. It continued outward in all directions from these centers. The result was the formation of a number of spherical bodies of tightly cemented sand grains scattered from the sandstone mass.
Had the cementation continued long enough, the spheres would have grown together and the huge rock would have become a homogenous mass. But before this could take place, erosion by wind, rain, wash and running water began to lower the surface.