What Is Lava Rock?

Rocks are popular with homeowners for a variety of applications. Lava rock is a generic term for a variety of igneous rocks that have versatile uses. Rocks are organic building materials that come in a variety of colors and textures to bring a bit of rustic nature to a home. Lava rock can be purchased from home improvement stores, nurseries and from landscape supply companies.

There are three types of rocks including igneous, sedimentary and metamorphic. Sedimentary rocks form from the compression of sediments or through precipitation in lakes, rivers, oceans and deserts. Igneous rocks form from volcanoes. Metamorphic rocks form when new layers of rock bury older layers and the old rock changes into a new type because of intense heat and pressure at depth. The term lava rock is a generic term for igneous rocks that form from magma beneath the ground or lava outside of the volcano. Magma and lava are the same thing, however, geologists use the term lava when the material is outside of the volcano.

Intrusive igneous rocks form when magma intrudes into cracks in the rocks surrounding the volcano and slowly cools over a long time. These types of rock include granite, diorite, peridotite and gabbro among others. Intrusive igneous rocks have visible grains. The mineral grains have a long time to grow as the magma slowly cools, which makes them easy to see in the rocks without magnification. Scientists call these textures medium- and coarse-grained.

Extrusive igneous rocks form when magma expels from a volcano during an eruption. Scientists call the material on the outside of the volcano lava. Extrusive igneous rocks have very small or no visible mineral grains because the lava cools very quickly on the outside of the volcano. Common extrusive rocks are basalt, obsidian, pumice and scoria. These rocks sometimes have a vesicular texture, which means that the rock has holes from air trapped in the lava as it cools. Obsidian has a texture with no grains. Scientists call these textures fine-grained and glassy.

Igneous rocks are common building and landscape materials. Intrusive igneous rocks, such as granite, are popular for floor tile, countertops and building blocks. Pumice an extrusive rock that is common in beauty products such as lava soap and pumice stones. Pumice and scoria also are common landscape materials. Gas grills also use scoria rocks to help distribute heat evenly throughout the grilling surface. The basalt rocks are common building materials and crushed stone can that can be used for paving roads. When lava rock is purchased from a landscape or home improvement store, it will mostly likely be basalt, pumice or scoria.