Knowledge Centre

What is slate?

Date : 20 December, 2020

Slate is a material derived from fine sediments, sometimes mud or occasionally from volcanic ash laid down millions of years ago and formed into layers known as bedding. As the pile of sediments thickened, the mud's original open structure is compacted to form shale or mudstone.

Flagstones are then created when these rocks are split on the bedding planes. However, for slate to form, the minerals in mudstones need to be transformed, which takes intense geological forces, such as those associated with mountain building.

Minerals such as quartz grains stretched and flattened, while clay minerals are recrystallised as platy minerals such as white mica and chlorite. Theses quartz minerals give the slate strength and durability. In contrast, the platy minerals form cleavage planes, which do not correspond to the bedding planes but allow the rock to be split into much thinner slabs suitable as roofing materials.

Back to Knowledge Centre

Subscribe to Our Newsletter