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Slate is a fine-grained, foliated metamorphic rock that is created by the alteration of shale or mudstone by low-grade regional metamorphism. It is popular for a wide variety of uses such as roofing, flooring and flagging because of its durability and attractive appearance.
Basalt is a dark-colored, fine-grained, igneous rock composed mainly of plagioclase and pyroxene minerals. It most commonly forms as an extrusive rock, such as a lava flow, but can also form in small intrusive bodies, such as an igneous dike or a thin sill.
An incredible example of natural basalt site is the Giant’s Causeway: an area of about 40,000 interlocking basalt columns, which is the result of an ancient volcanic eruption. It is located in County Antrim on the northeast coast of Northern Ireland and it was declared a World Heritage Site by UNESCO in 1986.