About Lava Rocks

Color

• While some specimens are nearly black, most are a dark gray. Some have been known to have a reddish or greenish hue.

Appearence

• Some basalt has vesicles, which are cavities created by air bubbles during formation, and some do not. The vesicles can look like the stretchy pores in bread or they can look like pock marks. The latter kind is found on those that are generally sold in stores as "lava rock." The texture can be somewhat grainy or glassy.

Formation

• Basalt is formed on or near the surface of the Earth; thus, they are called extrusive igneous rocks. Lava is the term given to magma when it breaches the surface in volcanic eruptions or fissures. The rock cools very quickly so the mineral crystals don't have much time to grow. This creates their distinctive appearance.

Contents

• Basalt is considered mafic, which means it's rich in magnesium and iron. Sometimes it contains feldspar, hornblende, pyroxene, biotite mica, quartz or olivine.

Practical Uses

• Basalt "lava rocks" have long been sold as decoration for gardens because of their distinct appearance. They can also be used in barbecue grills to help distribute heat evenly.