Mudstone

LL Demos & Labs: Rock Profile: Mudstone

This specimen is a dark purple in color and comes from an ancient seabed located in northern Utah. Mudstone is composed of the smallest sediment particles that are, by geological definition, 1/256 mm or smaller. These particles settle on top of one another for millions of years, layer after layer, and eventually the pressure caused by the weight of the sediment on the top of the pile drives the water out near the bottom, causing some of the minerals to recrystallize. What was once squishy, gooey mud at the bottom of an ancient ocean or pond is now stone.