[2] The rock known as Morton gneiss started out as a grey granite, formed about 3.5 billion years ago deep beneath the surface of the Earth.
[2] About a billion years later, two fragments of the Earth's crust collided at the future location of southwestern Minnesota, subjecting the granite to heat and pressure.
[2] When cut and polished, Morton gneiss shows bands and swirls of black, pink, and gray, with white flecks that sometimes look like galaxies and nebulae floating in space.
[3] About 100 million years ago, geologic forces slowly pushed Morton gneiss to the Earth's surface.
The glaciers that advanced and retreated across southwestern Minnesota starting two million years ago covered the rock with hundreds of feet of till.
[2] A vast body of water known as Lake Agassiz formed in southern Canada, Minnesota, and North Dakota.
Around the country it was used prominently in New York City, Detroit, Des Moines, Birmingham, Tulsa, Milwaukee, Hartford, and Cincinnati.
At the cemetery in Bird Island, Minnesota, a free-standing arch of Morton gneiss greets visitors.
Cloud granite, and Platteville limestone, Morton gneiss is one of Minnesota's chief contributions to the built environment.