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A cinder is a pyroclastic material. Cinders are extrusive igneous rocks. Cinders are similar to pumice, which has so many cavities, causing its low-density of 0.641g/cm^3 that allows it to even float on water. Cinder is typically brown, black, or red depending on its chemical content. A more modern name for cinder is scoria.
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 erosion resistance. In this context, they are referred to frequently with the name "lava rock".