Metamorphism, which is usually associated with tectonic compression within orogenic belts, can transform quartz-bearing sandstone into quartzite.
Sand deposits that eventually form sandstone are delivered to the basin by rivers, but they can also be delivered by the action of waves or wind. Some sand grains may be organic particles, such as sand and shell particles produced within the basin.
If the sandstone is tough enough, it could be crushed and used in construction projects. If it has a high quartz content, it may be crushed and used as a source of silica in glass manufacturing. Sandstone layers beneath the Earth's surface can act as aquifers for groundwater or reservoirs for oil and natural gas.
How Sandstone Forms
Sandstone is formed when sand is deposited and buried. This typically occurs offshore from river deltas, but desert dunes and beaches can also leave sandstone beds in the geologic record. The Grand Canyon's famous red rocks, for example, formed in a desert setting. Although fossils can be found in sandstone, the energetic environments in which sand beds form do not always favour preservation.
The pressure of burial and slightly higher temperatures allow minerals to dissolve or deform and become mobile when sand is deeply buried. The grains become more tightly knit, and the sediments are compressed into a smaller volume. This is the time when cementing material is transported into the sediment by fluids containing dissolved minerals. Red is caused by oxidising conditions.
Minerals of Sandstone
Sandstone is formally defined by particle size, but carbonate minerals do not qualify as sandstone. Because carbonate rocks are known as limestone and have their own classification, sandstone truly denotes a silicate-rich rock. (Calcarenite is a medium-grained clastic carbonate rock, also known as "limestone sandstone.") This distinction is reasonable because limestone is formed in clean ocean water, whereas silicate rocks are formed from sediment eroded from continents.
Because mature continental sediment consists of only a few surface minerals, sandstone is almost quartz. Other minerals, such as clays, hematite, ilmenite, feldspar, amphibole, and mica, as well as small rock fragments (lithics) and organic carbon (bitumen), add colour and character to the clastic fraction or matrix. Arkose is a sandstone that contains at least 25% feldspar. Tuff is a type of sandstone composed of volcanic particles.
Sandstone cement is typically composed of one of three materials: silica (chemically identical to quartz), calcium carbonate, or iron oxide. These can either infiltrate the matrix and bind it together, or they can fill in the gaps where there is no matrix.
Sandstone can range in colour from nearly white to nearly black, depending on the matrix and cement mix, with grey, brown, red, pink, and buff in between.
Sandstone Countertops Finishes
Sandstone countertops are available in a variety of finishes. Each of these finishes has benefits and drawbacks that should be considered. Let's look at some of the most popular sandstone countertop finishes.
The texture of sandstone is porous, soft, and easily scratched. If the sandstone countertop becomes wet, it can become extremely slippery. Moreover, sandstone will age over time; however, many homeowners prefer this aged appearance. Regular maintenance, such as annual or twice yearly sealing, will be required to keep your countertop looking new.
Leathered sandstone countertops highlight the natural characteristics of the stone. The leathering feels great and is very easy to clean. The process results in a stylish and functional textured surface.
Honed sandstone countertops produce a smooth surface. The finish brings out the beauty of the stone. It has a satin finish that does not reflect like polished natural stone countertops, but it does not have a flat, matte finish.
Polished sandstone has a glossy surface that reduces the porosity of the sandstone. This technique produces a smooth, slick surface that highlights the sandstone's naturally occurring colours and textures.