What Type of Rock Is Slate?
Commonly used in everything from billiard tables to chalk boards, the generally dark gray rock known as slate has been a used for a variety of applications for centuries. Does this Spark an idea?
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Type of Rock
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Of the three types of rocks in the geological world (sedimentary, igneous and metamorphic), slate is considered metamorphic.
Formation
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Metamorphic rock is formed when either sedimentary or igneous rock is subjected to extreme heat and pressure. Over time, these conditions can drastically alter the chemical and physical properties of the rock.
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Composition
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According to "The Columbia Electronic Encyclopedia," slate is composed primarily of micas, feldspars, quartz, clay and chlorites (see Reference 1).
Coloration
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Because ratios of composition vary, slate can be dark gray, brownish red or dark green, and it might be homogeneous in color or mottled depending on the source of the rock.
Uses
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Because of its tendency to form flat, thin sheets, slate is a commonly used rock type in roofing and interior finishing. Slate roof shingles have been used for hundreds of years and have a longer lifespan than common asphalt shingles.
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