Sand Roundness

A description of a sand grain according to how round are its edges and corners.

Roundness is typically described as either:
1. Very Angular: These have distinctly sharp edges and sharp corners; being exposed to minimal weathering. These particles can interlock very tightly, providing a very stable which can be suitable for inclusion in sub-bases which require to be well compacted to minimise movement.
2. Angular: These have sharp edges and corners, but less so than very angular particles; being exposed to some weathering. These will have a similar interlocking capability to very angular particles, offering limited drainage potential, but often leading to waterlogging.
3. Sub-Angular: Edges and corners are a transition between angular and sub-rounded but having a slightly angular and rougher appearance; being exposed to moderate weathering. These particles can provide a balance of stability and drainage, especially for high impact sports such as rugby and football but will typically require increased aeration and decompaction treatments in contrast to more rounded particles. Sub-angular particles can be suitable for use on the faces of golf bunkers which require good stability to prevent the sand from easily falling or washing down into the base of the bunker.
4. Sub-Rounded: Edges and corners start to become more rounded, which can be irregular in shape, with the particle becoming smoother, due to increased weathering. These particles provide a good balance between drainage and stability, due to some degree of interlocking of the particles, and are especially suitable for use in fine turf surfaces where player interaction with the sward surface is mild when compared with higher impact sports such as rugby and football.
5. Rounded: Distinctly rounded corners and edges, although the shape can be elongated, yet smooth; being well-weathered. These are good for drainage, although they can become unstable where root growth is weak.
6. Well Rounded: Corners and edges are not noticeable because the particle is generally a uniform round shape; being exposed to extensive weathering. These are good for drainage, especially overlaying pipe drains, although they can become unstable where root growth is weak.


See also Sand Shape and Sand Sphericity.