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What Is Slate?

What Is Slate?

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Slate can be said to be a foliated, fine-grained and homogenous type of metamorphic rock. It is formed from shale, which is an original kind of sedimentary rock. Shale as the lowest grade in the list of metamorphic rocks is made up of clay and in some cases volcanic ash. When shale is subjected to high temperature and pressure via low-grade metamorphism, a foliated, homogenous rock is formed where the layering may not be the same as the layering of the parent sedimentary rock. This is because the fossils originally present in the parent rock are mostly erased. This process achieves two things:1. It makes the rock be hard enough to tink or ring when subjected to hammer 2.The direction of the rock's cleavage becomes pronounced that it breaks and forms flat planes. If Slate is subjected to further metamorphism, it turns to phllite and then to scist.

Cutting of Slate can be achieved by striking it with a special type of tool. When this is done inside the quarry, most Slates will form fine, flat and smooth sheets of stone. In the time past, these flat-smooth sheets of stone have proven useful in roofing, floor tiles and other purposes. The colour of Slate, especially when seen is usually grey. However, Slate can be found in a variety of other colours even from a particular locality. For instance, Slates found in North Wales occur in a variety of shades of grey ranging from pale to dark. Some are also purple or even green.

The composition of Slate is mostly quartz and illite or in some cases muscovite. Sometimes it can also have some traces of biotite, hematite, pyrite or chlorite. Less often, you may find apatite, kaolin, tourmaline, graphite, magnetite or even feldspar in the Slate composition. Occasionally, as it is with the purple Slates of North Wales, there might be ferrous reduction reaction, which might form a sphere around the iron nuclei. This reaction may form light green spots on the Slate texture.

Slate roofs had been very popular. Sinks were once made with Slate. Stones for sharpening knives, tabletops and even walkways are made with Slate. Good quality Slate is used for paving stone and also a good material for a durable Slate roof tile, which are most useful for interior and exterior purposes. Slate has good electrical insulating and fireproof properties and thus was used in the early times for the construction of electric switchboards and also relay controls for big electric motors. It also makes for the best billiard tables. Slate was used for making blackboards and handheld writing tablets of which the tablets themselves have taken the name of the rock.

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