Carboniferous Millstone Grit

327 million years old

Around 325 million years ago a chain of mountain range stretched from mid Wales to Belgium. The rivers flowing from the mountains swept loads of sediment towards the sea. The first of sediments to accumulate along the shores were banks of pebbles and then, later, sand banks.

The mixture of pebbles and sand gave rise to conglomerate (Millstone Grit). The white blocks in this flower bed are examples of this rock.

Tough  and sparkling

This sandstone is visually distinctive as it is full of white quartz sand grains. Quartz is very hard, to the degree that crystals formed and parts of can be continually re-cycled.

Pure as Steel

The silica in the quartz is so pure that it can withstand very high temperatures. As a result, the Millstone Grit was quarried on a large scale in south Wales to help make furnace windows and fire bricks for the south Wales steel industry.

Where do these rocks come from? Carmel Quarry, Carmarthenshire