A cinder is a pyroclastic material. Cinders are extrusive igneous rocks. Cinders are similar to pumice, which has so many cavities and is such low-density that it can float on water. The color of cinder is brown.
The following geologic characteristics define a cinder:
Cinders have been used on track surfaces and roads to provide additional traction in winter conditions. Cinders are also employed as inorganic mulch in xeriscaping, because of excellent drainage properties and resistance to erosion. In this context, they are referred to frequently with the name "lava rock". This is why cinder is used in roads.