Marble

is a nonfoliated metamorphic rock resulting from the metamorphism of limestone , composed mostly of calcite (a crystalline form of calcium carbonate , Ca C O 3). It is extensively used for sculpture , as a building material, and in many other applications. The word "marble" is colloquially used to refer to many other stones that are capable of taking a high polish.Marble is a metamorphic rock resulting from regional or rarely contact metamorphism of sedimentary carbonate rocks , either limestone or dolostone , or metamorphism of older marble. This metamorphic process causes a complete recrystallization of the original rock into an interlocking mosaic of calcite , aragonite and/or dolomite crystals . The temperatures and pressures necessary to form marble usually destroy any fossils and sedimentary textures present in the original rock.Pure white marble is the result of metamorphism of very pure limestones. The characteristic swirls and veins of many colored marble varieties are usually due to various mineral impurities such as clay , silt , sand , iron oxides , or chert which were originally present as grains or layers in the limestone. Green coloration is often due to serpentine resulting from originally high magnesium limestone or dolostone with silica impurities. These various impurities have been mobilized and recrystallized by the intense pressure and heat of the metamorphism .

Travertine

is a sedimentary rock . It is a natural chemical precipitate of carbonate minerals ; typically Aragonite , but often recrystallized to, or primarily, Calcite .

The way travertine forms is basically this: calcium carbonate is deposited from the water of mineral springs or rivulets that are saturated with dissolved calcium bicarbonate . The spring water from which the calcium carbonate precipitates can be hot, warm or cold. The rate of deposition increases with the temperature of the water, or alternatively, when biotic material accelerates the process of precipitation. The ornate columns of travertine in caves are an example of an inorganic chemical sedimentary rock.

Travertine is often used as a building material . The largest building in the world constructed mostly of travertine is the Colosseum in Rome . Other notable buildings using travertine extensively include the Sacré-Coeur Basilica in Paris and the Getty Center in Los Angeles, California. The travertine used in the Getty Center construction was imported from Tivoli. The website of the Getty Center contains more information about the use of travertine in its construction, including some videos of travertine being quarried and cut for use. The stone is most widely used in Italy, Greece and Turkey.

Travertine is one of several natural stones that are used for paving patios and garden paths. It is sometimes known as travertine limestone, sometimes as travertine marble; these are the same stone, even though it is neither limestone nor marble . The stone is characterised by pitted holes and troughs in its surface. Although these troughs occur naturally, they suggest to some eyes that considerable wear and tear has occurred over many years. Some installers use a grout to fill these holes, whereas others leave them open -- travertine can even be purchased "filled" or "unfilled." It can be effectively polished to a smooth, shiny finish and comes in a variety of colors from grey to coral-red. Travertine is most commonly available in tile sizes for floor installations.

Travertine is one of the most frequently used stones in modern architecture , and is commonly seen as façade material, wall cladding, and flooring.

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 . The result is a foliated rock in which the foliation may not correspond to the original sedimentary layering. Slate is frequently grey in colour especially when seen en masse covering roofs. However, slate occurs in a variety of colours even from a single locality. For example slate from North Wales can be found in many shades of grey from pale to dark and may also be purple, green or cyan .

Slate can be made into roofing slates, also called roofing shingles , installed by a slater . Slate has two lines of breakability: cleavage and grain. This makes it possible to split slate into thin sheets. Fine slate can also be used as a whetstone to hone knives. Due to its thermal stability and chemical inertness, slate has been used for laboratory bench tops and for billiard table tops. In 18th and 19th century schools, slate was extensively used for blackboards and individual writing slates for which slate or chalk pencils were used. Because it is a good electrical insulator and fireproof , it was used to construct early 20th century electric switchboards and relay controls for large electric motors . British sculptor Stephen Kettle is notable for his use of slate to create statues housed in the Science Museum in London.

Slate tiles are often used for interior and exterior flooring , stairs and wall cladding. Tiles are installed and set on mortar and grouted along the edges. Chemical sealants are often used on tiles to improve durability and appearance, increase stain resistance, reduce efflorescence , and increase or reduce surface smoothness. Tiles are often sold gauged, meaning that the back surface is ground for ease of installation. Slate flooring can however be slippery when used in external locations subject to rain.

Slate tiles were used in 19th century UK building construction (apart from roofs) and in slate quarrying areas such as Bethesda there are still many buildings wholly constructed of slate. Slates can also be set into walls to provide a rudimentary damp-proof membrane . Small offcuts are used as shims to level floor joists.