Igneous rocks are formed from the solidification of molten rock material. There are two basic types. Intrusive igneous rocks crystallize below Earth's surface and the slow cooling that occurs there allows large crystals to form.Examples of intrusive igneous rocks are diorite, gabbro, granite, pegmatite, and peridotite.abbro is a coarse-grained, dark colored, intrusive igneous rock that contains feldspar, pyroxene and sometimes olivine. The specimen shown above is about two inches (five centimeters) across. Obsidian is a dark-colored volcanic glass that forms from the very rapid cooling of molten rock material.
McLennan County, Texas. McLennan County is a county located on the Edwards Plateau in Central Texas. As of the 2010 census, its population was 234,906. Its county seat is Waco. The U.S. census 2016 county population estimate is 247,934. The county is named for Neil McLennan, an early settler.
Waco, Texas. Tweet. Introduction to Waco, Texas. The Texas city of Waco, county seat of McLennan County, is located in the center of the Texas manufacturing and technology corridor, about 90 miles south of Dallas and 100 miles north of Austin.n 1856, Waco became incorporated as a city, and by the 1870s became a hub of commerce for the state of Texas with the arrival of several railroad lines. In 1886, Baylor University relocated to the city from Independence, Texas, merging with Waco University.