Cinder (geology)

Disambiguation: for the Killer Instinct character, see Cinder (Killer Instinct). For the post-rock band see Cinder. For the Dirty Three album see Cinder (album).

A cinder is a fragment of cooled pyroclastic material (lava or magma). Cinders are either intrusive igneous (magma cooled inside the earth) or extrusive igneous (lava cooled outside of the earth). Cinders are similar to pumice, which has so many cavities and is such low-density that it can float on water. Pumice or cinders are used in soap, xeriscaping, mulch, and rock gardens.

Volcanic eruptions such as this one can create cinders.

Characteristics

The following geologic characteristics define a cinder:

• Uncemented
• Vitric
• Having bubble-like cavities, called vesicles
• Measuring not less than 2.0 millimeters in at least one dimension
• Apparent specific gravity between 1.0 and 2.0

Typical cinders are red or black in color.

Uses

Cinders have been used on track surfaces and roads to provide additional traction in winter conditions. Cinders are also popularly 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 synonym "lava rock".

See also

• Cinder block
• Cinder cone
• Igneous rock
• Scoria
• Tephra