Apex Exports And Imports

Slate is a fine-grained, homogeneous, sedimentary rock composed of clay or volcanic ash, which has been metamorphosed (foliated) in layers (bedded deposits). Slate can be made into roofing shingles, because it has two lines of breakability: cleavage and grain. This makes it possible to split slate into thin sheets.

Slate is considered the lowest grade of metamorphic rock. It forms when shale, which consists of clay minerals like the sediments from which it formed, is put under pressure with temperatures of a few hundred degrees or so. Then the clays begin to revert to mica minerals. This does two things: first, the surface of slate has a sheen and reflectance typical of mica, and second, the rock gets a pronounced cleavage direction, so that it breaks along flat planes. This new cleavage plane is not always the same as the original sedimentary bedding planes, and any fossils originally in the rock are usually erased. With further metamorphism, slate turns to phyllite, then schist or gneiss.

Slate is usually dark, like this decorative specimen from a landscaping supply yard. High-quality slate is an excellent paving stone as well as a raw material for long-lasting roof tiles. Blackboards and handheld writing tablets were once made of slate, and the name of the rock has become the name of the tablets themselves.

Slate has a wild side. It's known mainly as the dependably dark gray material of roof tiles, flagstone walks, and old school blackboards. But new access to quarries in countries around the world now makes it possible to find slate in a subtle rainbow of colors as well. 

Technically, slate is a dense, fine-grain, clayey metamorphic rock that splits readily into thin but durable slabs. Minerals present in the rock cause its colors to vary widely--often within a single tile.

Slate is the Robert Redford of the stone world: Its rugged good looks and versatility allow it to play a wide range of roles; its mood can be rustic and casual or sleek and contemporary. This metamorphic rock works equally well for floors, hearths and fireplaces, backsplashes, counters, and patios.