Ironsand

Ironsand, also known as iron-sand or iron sand, is a type of sand with heavy concentrations of iron. It is typically dark grey or blackish in colour.

Iron sand from Phoenix, Arizona, attracted to a magnet

It is composed mainly of magnetite, Fe3O4, and also contains small amounts of titanium, silica, manganese, calcium and vanadium.[1]

Ironsand has a tendency to heat up in direct sunlight, causing temperatures high enough to cause minor burns. As such it forms a hazard in New Zealand at popular west-coast surf beaches such as Piha.[2]