Gravel mulch is a material used to landscape driveways, walking paths and flower beds. The different types of gravel mulch include crushed gravel, stone gravel, pea gravel and chips. Landscaping gravel differs from traditional mulch because it does not decay over time. Gravel mulch also helps prevent soil erosion and creates a firm foundation to walk or drive on.
Crushed gravel is a mixture of small rocks, silt, clay and sand. Landscaping with gravel mulch made up of this type of mixture is typically limited to driveways because it allows for compaction and can hold up under the heavy weight of vehicles. Crushed gravel is less expensive than other types of gravel mulch, which makes it preferable for the large areas driveways usually cover.
Stone gravel, on the other hand, is made up entirely of small pebbles. This type of gravel mulch is available in literally endless numbers of shades due to the variations in the stone the gravel is made from. Stone gravel is much more expensive than crushed gravel, so it is primarily used in smaller areas such as flower beds and around trees and shrubs.
The most common types of stone gravel are made from lava rock or river rock. Lava rock, as the name suggests, is the product of volcanoes. The most common lava rock is reddish brown and is much lighter and more porous than other types of gravel mulch. River rock is the smooth variegated pebbles gathered from river beds and sorted according to size.
Pea gravel is the term used to describe small pea-sized pebbles used in landscaping. It is often used to decorate walkways or patios. The two main ways pea gravel is sold is smooth and rough style. Smooth style pea gravel is the smallest river rocks gathered. After the sorting process, any tiny pieces are weeded out of the stone gravel product and sold as pea gravel.
The rough style pea gravel is made when stone quarries are blasting larger rocks into smaller, manageable sizes. The small pieces left over from this process are rough and sometimes jagged. They are sorted into varying sizes with the smallest ones used as pea gravel in landscaping applications.
Rock chips such as marble and brick are also used as gravel mulch. Marble chips are used most often in flower beds because the bright white chips contrast well with the greenery. Brick chips are used in driveways or walkways and are available in colors ranging from pale tan to deep red.