Scoria (or volcanic scoria) is a common igneous rock which is well known for its light weight and highly vesicular appearance (numerous empty holes and pockets). It goes by many other names including a'a lava and feather rock and is often found to be either a charcoal grey, black or deep red colour. Scoria is formed when magma within the earth begins to rise at an exit point on the earth surface, such as a volcano. Due to this, scoria tends to be basaltic or andesitic ni composition. As the magma begin to cool quickly, gasses within the magma/lava escape, leaving behind pockets within the lava, as it solidifies, so to, do these pockets and are known as vesicles. These vesicles give the rock a light weight, similar to pumice, however, unlike pumice, it tends to have a greater gravity and thus, does sink when placed in water. These particular rock specimens are from Italy and is available in 3 sizes, all samples come supplied in a card tray with an information label.