Answer:
Deep within the Earth's crust rocks can be put under huge pressures and temperatures are very high. These conditions can cause the minerals in the rock to change. This process is called metamorphism. Limestone can change into marble, shale and mudstones into slate, and igneous rocks like granite can turn into gneiss.
Step-by-step explanation:
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.