Liuskekivi

Liuskekivi, or slate, is a fine-grained metamorphic rock derived from shale or mudstone through low-grade regional metamorphism. It develops slaty cleavage, a planar splitting that lets the rock separate into thin, durable sheets.

The mineralogy is dominated by phyllosilicates such as muscovite, chlorite, and biotite, with quartz and calcite in minor amounts. Colors range from gray and green to red-brown or black, often reflecting impurities. During metamorphism, clay minerals realign perpendicular to compressive forces, producing the characteristic foliation. This cleavage enables the rock to be split with a knife or chisel into flat tiles, giving slate its traditional uses.

Slate has a long history in construction and design. It is widely used for roofing and siding because of its durability and weather resistance, as well as for flooring, countertops, tiles, and blackboards. It is quarried in belts around the world, including Europe and North America, with numerous historic and commercial quarries.

In geology, slate is distinguished from higher-grade metamorphic rocks by its low-temperature, low-pressure origin and well-developed cleavage rather than a strong foliation. Its performance depends on impurity content and jointing; water ingress and freeze-thaw cycles can affect durability in some climates.