How are Mineral Sands Formed?

A sandy beach

Rutile, ilmenite, zircon and monazite originally grew as crystals in igneous rocks such as granite, pegmatite and basalt and some metamorphic rocks.

Over millions of years, these igneous and metamorphic rocks were weathered and eroded, and the grains of quartz and other minerals in the rock, including rutile, ilmenite, zircon and monazite, were washed down to the sea by heavy rainfall and fast flowing streams.

The heavy minerals were then carried back up onto the beach by waves. As the waves washed up and down on the beach, they carried the lighter quartz grains with them back into the sea, leaving the grains of the heavy minerals rutile, ilmenite, zircon and monazite behind on the beach . Wind also helped to concentrate the heavy minerals by blowing away the lighter quartz sand. These processes were repeated many times over millions of years, eventually creating a large deposit of mineral sands on the beach.

As the sea level rose and fell over geological time, the shoreline moved further inland and then back again. As this happened, the deposits of mineral sand were covered by more sand and built up or eroded and redeposited elsewhere. This is why we sometimes find mineral sand deposits many kilometres inland and maybe as much as 50 metres below the surface.

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