Stone Types

Granite
Granite is a common and widely occurring type of igneous rock with a coarse granular texture. Granite is formed beneath the earth’s crust from molten rock under conditions of high pressure and temperature in areas of tectonic activity such as at mountain ranges. 

The stone owes its granular texture to the crystals that formed and grew as the molten rock cooled. The size of crystals is dependent on how quickly the molten rock cooled with slow cooling giving rise to large crystals. Granites vary widely in the size of their constituent crystals. Their colour depends on their chemical composition and can vary widely from fine grained black granites to coarse grained granites featuring white, pink, dark grey, black and even blue or green crystals.

Granite is hard and tough, and its hard wearing nature has made it a popular choice as a construction stone and also makes it ideal for use in worktops. Granite is heat and scratch resistant. While granite’s crystals are impermeable, the rock is porous as water can seep into the microscopic cracks between the crystals. When used as a worktop granite should be treated with a sealant to prevent water absorption and associated staining.

Limestone
Limestone is a sedimentary rock formed by reefs and rivers. It is typically granular with the grains formed from the skeletal fragments of marine organisms. Limestones often contain large fossil shell fragments. The grains are primarily composed of calcium carbonate and so are susceptible to acid. Depending on its composition it ranges in colour from off white, through grey to beige and light brown.

Limestone has been a popular building material through the ages as it is readily available, relatively easy to work and good for fine detail. Limestone is long-lasting and stands up well to exposure, which explains why many limestone ruins survive. However, it is very heavy, making it impractical for tall buildings, and relatively expensive as a building material. It is relatively soft but is widely used as flooring, cladding and for vanity tops in bathrooms.

Untreated limestone is porous and will absorb water and stain easily. Due to its calcium carbonate composition, limestone is vulnerable to damage from contact with acidic substances such vinegar and citric acid. If used as a countertop limestone needs to be regularly sealed to protect it.

Marble
Marble is a Metamorphic rock formed when the calcium carbonate in limestone or dolomite dissolves and recrystallises under the increased pressure and heat that the rock experiences as it is buried deeper over time. Marbles are composed of interlocking crystals of calcium carbonate with the size of the crystals giving it a coarse or fine grained texture. Brilliant white marble, such as Thassos, is formed from the recrystallisation of limestones that are pure calcium carbonate. The colouring in marble is caused by minerals other than calcium carbonate in the source rock. These other minerals often concentrate in layers producing a veined appearance.

Marbles occur in a wide variety of colours including white, grey, pink, green, brown and black. Marble has been the preferred material for sculptors since classical times and has been widely used in construction and as a flooring material.

Unsealed marble is porous and absorbs water. If a liquid is left to pool on a marble surface it will be absorbed and may leave a stain.

Marble dissolves in acid and so can be damaged by a variety of substances such as vinegar and citric acid. Contact with acid will remove the polish from unsealed marble. To protect marble it needs to be regularly treated with sealant.

Onyx
Onyx is a banded variety of the silicate mineral chalcedony. Due to its crystalline nature it is fragile and vulnerable to shattering. Onyx is a semiprecious material and is used in jewellery as well as in interior decoration. Onyx is available in a wide variety of colours including white, brown, green, orange, yellow and black. It is translucent and is often backlit when used as counter cladding or wall panelling to produce stunning effects.

Quartz Composite
Quartz Composite is a generic term used to refer to the wide variety of manufactured stones that are primarily composed of crushed quartz crystals. Pigments and other materials are added to give colour to the stone and bonding agents are added to hold it together. There are a large number of quartz composite manufacturers. We are not tied to any manufacturer and are approved fabricators for a wide range of quartz composite stone including Arenastone, Caesarstone, Cambria, Cimstone, Compac, CRL, Quarella, Radianz & Silestone. There is an enormous choice of different colours and textures available.

Quartz composite is typically hard, non-porous, stain and scratch resistant. With no calcium carbonate content the stone does not share marble and limestone’s vulnerability to acid. Quartz composite requires low maintenance making it a popular choice for kitchen worktops.

Quartzite
Quartzite is a naturally occurring metamorphic rock. Quartzite is formed when sandstone is subjected to high pressure and temperature and the sandstone’s quartz grains dissolve and recrystallise in an interlocking mosaic like structure. Pure quartzite is typically white to grey coloured but the presence of other minerals can produce yellow, orange, pink, red, green and blue quartzites.

Quatrzite is a very hard material, impermeable and so is scratch and stain resistant.

Sandstone
Sandstone is a sedimentary rock composed of cemented grains of silicate material (either quartz or feldspar). These grains are the eroded fragments of rock or crystal. They are formed by rivers, lakes, deltas, beaches and offshore sand bars. The grains are first deposited as water or air currents slow and then compacted as they are buried over time. The buried grains are later cemented typically by silica or calcium carbonate from dissolved fossil matter. The size of sandstone’s constituent grains can range from 0.05 to 2 mm in diameter. Depending on the extent of cementing sandstone is liable to crumble and where calcium carbonate is the cementing agent it is vulnerable to acid. Sandstone is extremely porous. Sandstone is relatively soft and easy to carve making it a popular building and paving material since ancient times. Sandstone is typically tan or yellow in colour with darker reddish varieties also occurring when iron oxide is present.

Slate
Slate is a fine grained metamorphic rock formed when shale is subjected to pressure and temperature. It is composed of clay or volcanic ash and is foliated or layered which produces its characteristic cleavage. The foliation is produced by the differential pressure the rock experienced as it is squeezed and stretched. Slate is fissile and can be cut into sheets. Slate has very low water absorption making it practically water proof, which together with its fissile nature explains why it is the ideal roofing material. While it is also a popular floor tiling material, its water proof nature can make it very slippery underfoot when used outdoors. Slate typically varies from light to dark grey in colour but light green and cyan varieties can also be found.

Chemical sealants are often used on tiles to improve durability and appearance, increase stain resistance, and increase or reduce surface smoothness.

Travertine
Travertine is a distinctive banded variety of limestone formed along streams, particularly where there are waterfalls and around hot or cold springs. The stone is characterised by pitted holes and troughs in its surface which are created by escaping gas bubbles. Although these troughs occur naturally, they suggest signs of considerable wear and tear over time. It can also be polished to a smooth, shiny finish, and comes in a variety of colours from grey to coral-red. Travertine is most commonly used as floor tiling but is also available in slabs for use in facades and wall cladding.

Travertine can be cut perpendicular to the bedding plain that exposes a linear pattern known as the vein cut or it can be cut across the bedding plain also known as the cross cut. Cross cuts show off the cloud like patterns in the stone.

The most popular finish for Travertine is a honed finish. The holes on the stone are filled during production with either cementitious, epoxy or polyester fillers. It is then honed with suitable diamond abrasives into a non-reflective but smooth surface. Honed material is largely scratch-resistant as a result of it lacking a glossy surface like that of polished stone. This superior scratch resistance makes honed material more robust for higher-traffic surfaces. A honed finish, however, makes the stone more porous so it will soak up liquids faster and easier than a polished travertine if left unsealed. Travertine is also available with polished or tumbled finishes.

Travertine is often used as a building material. In Italy, well-known travertine quarries exist in Tivoli and Guidonia Montecelio, where the most important quarries since Ancient Roman times can be found. The Romans built temples, aqueducts, monuments, bath complexes, and amphitheatres such as the Colosseum from travertine. It was used to build the famous Colonnade of St. Peter's Square in Rome in 1656-1667. Michaelangelo chose travertine for the external ribs of the dome of St Peter's Basilica. Travertine derives its name from the former town, known as Tibur in ancient Roman times. Travertine is frequently used in modern architecture where it is used for façades, wall cladding, and flooring.

Italy is the dominant supplier of travertine and held a near-monopoly until the 1980s. Significant quantities are now quarried in Turkey, Iran, Mexico, and Peru.
By virtue of its limestone nature, untreated travertine is porous, highly water absorbent and vulnerable to staining and etching from acidic material. Regular sealing is essential to protect the stone.