Where scoria is not available, a lightweight aggregate can be produced by heating shale in a rotating kiln under controlled conditions. With the proper type of shale, the material will have the properties, appearance, and vesicles of scoria. It is sold under the name “expanded aggregate,” “expanded clay,” or “grow rocks” and used for the…

One of the main uses of scoria is in the production of lightweight aggregate. The scoria is crushed to desired sizes and sold for a variety of uses. Concrete made with scoria typically weighs about 100 pounds per cubic foot. This is a weight savings compared to concrete made with typical sand and gravel that…

A vesicular igneous rock that is very similar to scoria is pumice. There are a few differences that can be used to distinguish them. First is their color. Scoria is almost always black or dark gray to reddish brown, while pumice is almost always white to light gray to light tan. This color difference is a…

Have you ever slowly opened a bottle that contains a carbonated beverage and watched the gas bubbles form on the walls of the bottle? Then as the seal on the bottle is broken, the bubbles grow larger and a hiss of gas escapes from the bottle, followed by a rush of foam. The depressurization and…

Some newly erupted lava flows contain abundant dissolved gas. The gas bubbles in the flow move upwards towards the surface in an attempt to escape while the lava is still molten. However, once the lava starts to solidify, the bubbles are trapped in the rock. These trapped gas bubbles are known as vesicles. If the upper portion…

Most of the scoria falls to the ground near the vent to build up a cone-shaped hill called a “cinder cone.” Cinder cones are generally small volcanoes produced by brief eruptions with a total vertical relief of less than a few thousand feet. They are usually very steep because scoria has an angle of repose…

Scoria forms when magma containing abundant dissolved gas flows from a volcano or is blown out during an eruption. As the molten rock emerges from the Earth, the pressure upon it is reduced and the dissolved gas starts to escape in the form of bubbles. If the molten rock solidifies before the gas has escaped,…

Scoria is a dark-colored igneous rock with abundant round bubble-like cavities known as vesicles. It ranges in color from black or dark gray to deep reddish brown. Scoria usually has a composition similar to basalt, but it can also have a composition similar to andesite. Many people believe that small pieces of scoria look like the ash produced in a…