Granite is a course crystalline igneous rock formed by the slow cooling of hot molten rock deep within the earth. All granite contains quartz and feldspar and a small amount of at least one of several other minerals (biotite, muscovite, hornblende etc.). The only granite native to Kansas and exposed at surface outcrops on a low hill or ridge along U.S. 75, eight miles south of Yates Center in Woodson County. The granite consists largely of cream to white colored feldspar and bluish quartz and is badly weathered. Most of granite that is seen at this locality is in the form of residual boulders. The granite that is exposed, probably does not represent an igneous body of great depth. Drilling has revealed peridoite and metamorphosed and unmetamorphosed Pennsylvanian sediments below the surface. The granite has been age-dated as Precambrian, whereas the peridotite is Cretaceous. The granite apparently ripped loose at depth and brought up to the site by the eruptive force of younger igneous rocks.
Tremendous quantities of granite and granite-like rock occur
in the subsurface of "basement" rocks of Kansas, upon
which the oldest Paleozoic sediments were deposited. It is found
at depths of 600 feet to several thousand feet. It is closest
to the surface in Nemaha County.
Many varieties of granite can be found in the glacial till of
northeastern Kansas and along prehistoric stream valleys in western
Kansas.
Peridotite is a medium to course grained basic igneous rock containing phlogopite mica below the granite exposure in Woodson County. It outcrops in sill-like mas about one mile long and ¼ mile wide. At the surface, the rock is altered to a yellowish mass of clay studded with vermiculite.
Kimberlite, a form of peridotite is found in several locations in Riley County. Kimberlite is called intrusive igneous rocks because they were forced into other rocks below the surface of the Earth. In appearance the rock is soft, dull grey-green and is cut by thin white veins of calcite and magnetite. formed much like a volcano, as igneous rocks wells up to the surface from deep underground.
Volcanic Ash consists of tiny glass or congealed lava fragments that have been blown into the atmosphere during eruptions of volcanoes such as Mount St. Helens in May, 1980. It is a type of extrusive rock (forced out of extruded onto the Earth's surface). Volcanic ash in Kansas is found along with sedimentary deposits of Tertiary and Quaternary ages and is 20 feet thick in some places. Ash can be distinguished from other rocks by its white to bluish-gray color. Its glassy surfaces sparkle in the sund and its particles do not dissolve in water as do particles of limestone and chalk.
No volcanoes existed in Kansas during the time of the volcanic ash deposits, so a source outside the state must have been responsible. Most of the Kansas ash was probably carried by the wind from volcanoes in New Mexico, a massive eruption in Yellowstone, 600,000 years ago and from the Long Valley caldera in California. Once in Kansas, some of the ash was carried for short distances by streams and was deposited in quiet bodies of water such as ponds, burying pond grassses and snails in the clays at the bottom. Ash occurs abundantly in central and western Kansas and has been found as far east as Nemaha, Douglas, Johnson, and Chautauqua counties. Its uses includes: in toothpaste and powders, as abrasives, cleaning compounds, glazes for pottery, in filters, and in the manufacture of cement and road asphalt. Volcanic ash is mined near Calvert in Norton County.
Basalt is an extrusive igneous rock that pours out of
a volcano rather that being blasted out as in the case of volcanic
ash. It is usually black to dark gray and sometimes has a ropy
appearance. No basalt native to Kansas exists near the surface,
however, parts of the Dakota Formation (Coronado Heights, Saline
County) with its ropy appearing, dark brown sandstone has been
mistakenly identified as basalt. This structure was caused by
the chemical deposition of iron oxide in the sand. Boulders and
pebbles of basalt occur in stream valleys in the southwestern
part of the state and in the glacial till of the northeastern
glaciated region.