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Here you will find the most common questions related to natural slate and our selection of products.

What is natural slate?

Slate is derived from fine-grained sediments such as mud or occasionally volcanic ash laid down millions of years ago in layers known as bedding. As the pile of sediments thickened, the original open structure of the mud was compacted into a mudstone or shale.

These rocks are easily split on the bedding planes and are referred to as flagstones. However, for a slate to form, subsequent intense geological forces associated with mountain building are required, during which the minerals present in the original mudstone are metamorphosed.

 Some minerals, such as quartz grains, are flattened and stretched, while clay minerals are recrystallised as platy minerals: white mica and chlorite. The quartz minerals give the slate strength and durability, while the platy minerals form cleavage planes, which do not correspond to the bedding planes, but which allow the rock to be split into much thinner slabs suitable as roofing material. Differences in the composition of the original mudstone and the degree of metamorphism affect the quality of the slates thus produced.

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