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Materials - Slate

Slate is a dense, fine-grained, fissile rock, formed by the metamorphism of shale or clay, or more rarely of igneous rocks.


The process of metamorphism results in consolidation of the original rock and in formation of new cleavage planes along which slate characteristically splits into thin, broad sheets. Many rocks that show “slaty cleavage” are by extension loosely called slate. True slate is hard and compact and does not undergo appreciable weathering.
The basic minerals comprising slate are quartz and muscovite, a kind of mica; biotite, chlorite, and haematite are often present as accessory minerals, and apatite, graphite, kaolin, magnetite, tourmaline, and zircon may occur as minor accessory minerals.


Slate is commonly bluish-black or grey-black in colour, but red, green, purple, and variegated varieties are known; it is quarried in Wales, France, Germany, and the United States. Slate is quarried usually in open pits and rarely in underground workings. The stone splits best when it is “green”, or freshly taken from the quarry. Slate, whilst at one time was almost exclusively employed as a roofing material, is today used for paving stones, flooring, and wall cladding, both internally and externally.


We include below a palette of some of our most popular materials. This display is not extensive as there are many others to choose from that are available to us from worldwide resources.