Mosaic Canyon was named for a rock formation known as the “Mosaic Breccia.” Breccia is the Italian word meaning “fragments”. This formation is composed of angular fragments of many different kinds of parent rock, and it can be seen on the floor of the canyon just south of the parking area. The most common rock formation in the canyon is the Noonday Dolomite. This limestone is rich in magnesium andformed750to900 million years ago when the area was part of the Pacific Ocean. This sedimentary material was later buried to great depths by younger materials and was subjected to pressures and temperatures exceeding 1000 degrees Fahrenheit. As a result, much of the limestone was altered, or metamorphosed, into marble. Subsequent uplift and erosion have since re-exposed these metamorphic rocks.