Fragum erugatum, well known to those with an interest in marine life, is the reason for our visit to a spectacular location this morning. Situated on Shark Bay Road 44KM southeast of Denham is Shell Beach – all 66KM of it.

Cockles

For thousands of years the Fragum cockle has been the exclusive shellfish in this area of the L’haridon Bight. With no predators, hypersaline water and no competing species the Fragum cockle has proliferated and the result is a beach made of tiny shells, trillions of them – in places to a depth of 10-metres. It is one of only two beaches in the world made entirely of shells.

Blindingly bright and looking more like snow, it requires a closer look to see that these really are shells.

Growing to a maximum size of 14mm the cockles bury themselves in the seabed with over 4000 sharing the same square metre before ultimately washing up on the shore.

Coquina

Until Shell Beach became World Heritage Listed it was briefly quarried to produce ‘stone’ blocks.

After being washed ashore for more than 4,000-years, the deeper layers of shell become highly compressed. Rain, absorbing carbon dioxide from the atmosphere, creates a weak acid, which leaches through the layers of shells producing calcium carbonate and cementing the compacted shells into a stone known as Coquina.

The stone was hand cut into large blocks and used for building material. A good example of Coquina stone construction is the Old Pearler Restaurant in Denham.

The remains of the quarry still stand and are clearly visible from the beach but are now restricted access though some stones are still being cut but only for repairing existing Coquina stone buildings.

Take a dip

The water in the bay has twice the salinity of normal sea water, which makes it very easy to float in but your skin will get a generous crispy coating of salt in the process.