Rock City is a park located on hillsides overlooking the Solomon River in Ottawa County, Kansas.

[7] Shaffer[5] was the first person to map the distribution of these boulders at Rock City and investigate their petrography in detail.

[8] The host rock, which contained these spherical boulders, consists of well-sorted, medium-grained, highly porous, and friable sandstone.

Being only weakly indurated by small amounts of iron oxide, sometimes seen as Liesegang rings (banding) at Rock City, it is considerably softer and very much more easily eroded than the calcite concretions.

The carbon and calcium comprising these concretions came either from marine limestone, shells, anhydrite, or some combination of these in addition to bicarbonate derived from oxidized methane from strata outside of, but hydrologically connected to, the Dakota Sandstone.

After the formation of the concretions, differential erosion of the considerably softer sandstone surrounding them exposed as free-standing boulders.