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For example, roof slate referred to shale above a coal seam, and draw slate referred to shale that fell from the mine roof as the coal was removed. [ 16 ] The British Geological Survey recommends that the term "slate" be used in scientific writings only when very little else is known about the rock that would allow a more definite classification.
Slate – Metamorphic rock - A low grade metamorphic rock formed from shale or silt; Suevite – Rock consisting partly of melted material formed during an impact event – A rock formed by partial melting during a meteorite impact; Talc carbonate – A metamorphosed ultramafic rock with talc as an essential constituent; similar to a serpentinite
Slate has been quarried in north Wales for almost two millennia with the Segontium Roman fort at Caernarfon being roofed by local slate in the late second century. Export of slate has been carried out for several centuries, which was recently confirmed by the discovery in the Menai Strait of the wreck of a 16th-century wooden ship carrying finished slates.
Metamorphic rocks are formed when existing rock is transformed physically or chemically at elevated temperature, without actually melting to any great degree. The importance of heating in the formation of metamorphic rock was first noted by the pioneering Scottish naturalist, James Hutton, who is often described as the father of modern geology ...
A gneiss has visible bands of differing lightness, with a common example being the granite gneiss. Other varieties of foliated rock include slates, phyllites, and mylonite. Familiar examples of non-foliated metamorphic rocks include marble, soapstone, and serpentine. This branch contains quartzite—a metamorphosed form of sandstone—and hornfels.
The most important slate deposits in Wales are the Cambrian deposits south of Bangor and Caernarfon and the Ordovician deposits around Blaenau Ffestiniog. [7]The slate deposits of Wales belong to three geological series: Cambrian, Ordovician and Silurian.
Few important names in slate are Jak Black, Silver Shine, Silver grey, Panther, Deoli Green, Peacock, Peacock Multi, Kund Black, Kund Multi, and so on. Being to some extent fragile in nature, it is good for interior use only and can be used in even as a washboard.
It is home to a number of National Nature Reserves (NNRs), sites of special scientific interest (SSSIs), five areas of outstanding natural beauty (AONBs) and three national parks. Wales has many protected areas including three national parks: Snowdonia, Brecon Beacons and Pembrokeshire Coast.