Would you like to teleport to sandy dunes while sipping morning coffee in your kitchen? Then you'll love a sandstone wall or sandstone worktop. Sandstone slabs in the shades of yellow, orange, grey or red are like large sand dune paintings. If you have grown up in a northern country, they might remind you of the seashore smelling pines and amber. If you come from the South, you might even feel the desert wind to caress your cheek.
As you have already guessed, sandstone is made up of tiny grains of sand. Before turning into sandstone, those grains have travelled along the rivers and danced in the desert winds. When the nature's forces let them be, they lay down still in crevices and on the river bottoms. With time, more sand grains lay over them and pressed them, while minerals cemented them together. Years passed, such sand piles turned into solid rocks. The spectacular arches, pillars and other rock formations in the deserts are pure sandstone.
Sandstone is easy to work, which makes it convenient as building and paving material. Sandstone is also slip-resistant. However, outdoors sandstone can darken and discolour from moisture. This beautiful natural stone was used to build temples in Ancient Egypt. Large sandstone quarries from the times of pharaohs can still be visited in Aswan today. The world's most famous sandstone masterpiece is the ancient city of Petra in Jordan.
Sandstone hardness is between 5.5 and 7 on the Mohs scale. It can be softer or harder, depending on the clast and cement composition. The more calcium carbonate sandstone contains, the harder and more resistant to weathering it is. Generally, the lower the porosity of sandstone, the more resistant it is. Pure quartz sandstone with quartz content of over 90% is very hard and resistant, its physical properties can compare to those of granite. Countertops and stairs made of such sandstone will be strong, durable and resistant to frost. Sealing sandstone is highly recommended as stain removal can be limited due to its porosity later.
Sandstone is a sedimentary rock made up of cemented sand grains. When the sand is deposited in a river bed or is blown around by the wind in a desert, mineral sediments get trapped between the particles and hold them together. To turn a mountain of sand into a stone, pressure is also needed. It goes something like this: first the particles stop rolling down the river bed or desert, and then more layers start to accumulate on top of them, one by one. As the layers are compressed by the layers above them, the minerals between the grains gradually begin to cement them.
Sandstone is a sedimentary rock formed under oceans, lakes and rivers, where sand has been laid down and buried. It is composed of cemented sand grains, rock fragments, minerals and organic material. The cementing material that binds sand grains together and occupies spaces between them is typically silica and calcium carbonate, which are often derived either from dissolution or from alteration of the sand after it was buried. Sandstone colour is usually yellow, red, brown or grey to white reflecting the variation in mineral content and cement.
The cements that bind the grains together are calcite, clay and silica. The grey and white sandstone grains are quartz, the black ones are particles of dirty coal and shale and the brown ones are mottled clay minerals. Some sand particles are organic in origin, such as crumbs of shells crushed by waves.
Sand grains become mechanically compacted at depths of less than 1000 m. Deeper down, they become chemically denser. Chemical compaction takes place at the points of contact between the grains as they are under the greatest pressure. The stressed mineral is more soluble than the rest of the grain, causing the contact points to dissolve and fuse. The strongest cementation of sandstone occurs at depths of 2 000 to 5 000 metres.
The sandstone that forms in the depths is washed away by river currents and blown away by desert winds. It is usually opaque, with a rough surface. The main constituents of sandstone are the minerals quartz and feldspar, the proportions of which determine its hardness and resistance to weathering. If sand particles are deposited close to the original weathering rock, the composition of the sandstone is similar to that of the latter. Conversely, the greater the distance between the source rock and the sand accumulation site, the more the composition of the sandstone changes.
Impurities give the sandstone its different shades and patterns. Slabs of this stone can have grey, yellowish, orange, brown and even black tones. In some deserts, iron oxide is abundant, which colours the sandstone a deep red, and if manganese is present, the sandstone turns purple.
There are three types of sandstone:
Arkose. These sandstones have a high content (>25%) of shale and are similar in properties to granite. Arkosic sandstones form desert arches and picturesque columns.
Quartz. These sandstones contain a high proportion (>90 %) of quartz. These sandstones are also known as ortho quartzites or beach sand.
Lithic. These sandstones contain a high clay or silt content. They are also known as grey stones or bluestones.
Sandstone is found all over the world. It is one of the most common types of sedimentary rock. The sand that forms sandstone is carried by river currents, waves and wind. Intercontinental basins and ditches on the margins of continents are common places for sand deposition. Deserts are rich in sandstone. Red sandstones are found in the USA, England and Wales, Central Europe and Mongolia. In Egypt, there are huge sandstone quarries from the time of the pharaohs.certain colours have been strongly identified with certain regions.
The sandstone is mined using conventional drilling and blasting methods. After blasting, the sandstone blocks are lifted by a front-end loader, placed on trucks and transported to the cutting plants. Large chunks can also be separated from the deposit by drilling a large number of parallel vertical and horizontal channels into the formation using special machines. Wedges are driven into them to separate the block. Large blocks are cut with diamond-bladed chainsaws several metres long. Water jet cutting is also possible.
Interior and exterior walls
Sandstone is a particularly porous stone. If not impregnated before use, it absorbs liquids and discolours quickly. Sandstone worktops and other interior fittings can be washed in warm, soapy water and then wiped well. When cleaning the surface, pay attention to whether the water soaks into the sandstone or stays on top. If it does, it is time to impregnate the stone.
Do not wash sandstone surfaces with household cleaners unless they are designed for cleaning natural stone. Acidic cleaners corrode the surface of the stone, which can permanently change the texture and colour of the worktop. Water should not be left standing on the surface of sandstone as the stone will gradually absorb it. Most liquids can stain sandstone, but wine, fruit juices and coffee are particularly harmful.
If you can't get the stains off the worktop with soapy water, make a baking soda porridge. Add a couple of tablespoons of bicarbonate of soda to a small bowl and a few drops of water. Apply the mixture to the stain and, after a few minutes, wipe it off with a soft-bristled brush.
Outdoor sandstone terraces, stairs and facades can be cleaned of moss and algae with bleach. Mix equal parts of bleach and water and apply to the panels. Leave for about 30 minutes and rinse with a brush or hose. Do not use a high-pressure hose as you may damage the stone.