Slate

Slate is a fine-grained, foliated, homogeneous metamorphic rock derived from an original shale-type sedimentary rock composed of clay or volcanic ash through low-grade regional metamorphism. It is the finest grained foliated metamorphic rock. Foliation may not correspond to the original sedimentary layering, but instead is in planes perpendicular to the direction of metamorphic compression.

Formation

Slate is formed when sedimentary rock (shale) is subjected to high pressure and temperature. This process, known as metamorphism, changes the clay minerals in shale to mica minerals, which are more stable under the new conditions. The mica minerals align themselves perpendicular to the direction of pressure, creating a foliated texture in the rock.

Uses

Slate has been used for many purposes over the centuries. Its resistance to weathering and attractive appearance have made it a popular choice for roofing and flooring. It is also used in billiard tables and laboratory bench tops due to its durability and natural cleavage properties.

Types of Slate

There are several types of slate, including black, green, red, purple, and gray. The color of the slate is determined by the minerals present during its formation. For example, red slate is colored by the presence of iron oxide, while green slate is colored by the presence of chlorite.

See Also

• Metamorphic rock
• Shale
• Mica
• Foliation (geology)

Slate Resources
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