1.a sedimentary rock consisting of sand consolidated with some cement (clay or quartz etc.)
SandstoneSand"stone` (?), n. A rock made of sand more or less firmly united. Common or siliceous sandstone consists mainly of quartz sand.
☞ Different names are applied to the various kinds of sandstone according to their composition; as, granitic, argillaceous, micaceous, etc.
Flexible sandstone (Min.), the finer-grained variety of itacolumite, which on account of the scales of mica in the lamination is quite flexible. -- Red sandstone, a name given to two extensive series of British rocks in which red sandstones predominate, one below, and the other above, the coal measures. These were formerly known as the Old and the New Red Sandstone respectively, and the former name is still retained for the group preceding the Coal and referred to the Devonian age, but the term New Red Sandstone is now little used, some of the strata being regarded as Permian and the remained as Triassic. See the Chart of Geology.
Aquia Creek sandstone • Aztec Sandstone • Beacon sandstone • Beaver River sandstone • Big Clifty Sandstone • Birdsong Sandstone • Bluff Dale Sandstone • Bowdoin Sandstone • Broome Sandstone • Bushveld Sandstone Formation • Calciferous sandstone • Cape Sebastian Sandstone • Castlegate Sandstone • Cedar Mesa Sandstone • Coalura Sandstone • Coconino Sandstone • Colalura Sandstone • Cutbank Sandstone • Dakota Sandstone • Double-arch Sandstone Bridge • Eagle Sandstone • Elbe Sandstone Mountains • Entrada Sandstone • Festningen Sandstone • Forest Sandstone Formation • Glauconitic Sandstone • Guettioua Sandstone • Hawkesbury sandstone • Horsethief Sandstone • Hutton Sandstone Formation • Kisbey Sandstone • Lithic sandstone • Lompico Sandstone • Lossie Mouth Sandstone Formation • Medicine Hat Sandstone • Navajo Sandstone • New Red Sandstone • Nubian Sandstone • Nubian Sandstone Aquifer System • Old Red Sandstone • Old Red Sandstone Continent • Old Red Sandstone continent • Operation Sandstone • Phillips Sandstone • Point Lookout Sandstone • Precipice Sandstone • Red sandstone • Sandstone (disambiguation) • Sandstone Amphitheater • Sandstone Charter Township, Michigan • Sandstone Dibbler • Sandstone Estates • Sandstone Gold Mine • Sandstone Point, Queensland • Sandstone Ranch • Sandstone Ranch (Nevada) • Sandstone Retreat • Sandstone Shrike-thrush • Sandstone Township • Sandstone Township, Pine County, Minnesota • Sandstone Trail • Sandstone Universities • Sandstone Valley, Calgary • Sandstone night lizard • Sandstone university • Sandstone, Michigan • Sandstone, Minnesota • Sandstone, West Virginia • Sandstone, Western Australia • Saxon-Bohemian Chalk Sandstone Region • Shire of Sandstone • St. Peter Sandstone • Sydney sandstone • Taber Sandstone • Table Mountain sandstone • Torridonian sandstone • Tumblagooda sandstone • Upper Karroo Sandstone Formation • Valtos Sandstone Formation • Vaqueros sandstone • Wingate Sandstone
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Prepared sample of sandstone
|Typically quartz and/or feldspar; lithic fragments are also common. Other minerals may be found in particularly immature sandstone.|
Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any colour, but the most common colours are tan, brown, yellow, red, gray, pink, white and black. Since sandstone beds often form highly visible cliffs and other topographic features, certain colours of sandstone have been strongly identified with certain regions.
Rock formations that are primarily composed of sandstone usually allow percolation of water and other fluids and are porous enough to store large quantities, making them valuable aquifers and petroleum reservoirs. Fine-grained aquifers, such as sandstones, are more apt to filter out pollutants from the surface than are rocks with cracks and crevices, such as limestone or other rocks fractured by seismic activity.
Sandstone is mined by quarrying. It is sometimes found where there used to be small seas. It is usually formed in deserts or dry places like the Sahara Desert in Africa, the Arabian desert in the Middle East and the Australian desert (including Sydney). In the western United States and in central Australia, most sandstone is red.
Sandstone is converted into quartzite through heating and pressure usually related to tectonic compression within orogenic belts.
Sandstone has been used for domestic construction and housewares since prehistoric times, and continues to be used.
Sandstone was a popular building material from ancient times. It is relatively soft, making it easy to carve. It has been widely used around the world in constructing temples, cathedrals, homes, and other buildings. It has also been used for artistic purposes to create ornamental fountains and statues.
Some sandstones are resistant to weathering, yet are easy to work. This makes sandstone a common building and paving material. However, some that have been used in the past, such as the Collyhurst sandstone used in North West England, have been found less resistant, necessitating repair and replacement in older buildings. Because of the hardness of individual grains, uniformity of grain size and friability of their structure, some types of sandstone are excellent materials from which to make grindstones, for sharpening blades and other implements. Non-friable sandstone can be used to make grindstones for grinding grain, e.g., gritstone.
Sandstones are clastic in origin (as opposed to either organic, like chalk and coal, or chemical, like gypsum and jasper). They are formed from cemented grains that may either be fragments of a pre-existing rock or be mono-minerallic crystals. The cements binding these grains together are typically calcite, clays, and silica. Grain sizes in sands are defined (in geology) within the range of 0.0625 mm to 2 mm (0.002–0.079 inches). Clays and sediments with smaller grain sizes not visible with the naked eye, including siltstones and shales, are typically called argillaceous sediments; rocks with greater grain sizes, including breccias and conglomerates are termed rudaceous sediments.
The formation of sandstone involves two principal stages. First, a layer or layers of sand accumulates as the result of sedimentation, either from water (as in a stream, lake, or sea) or from air (as in a desert). Typically, sedimentation occurs by the sand settling out from suspension; i.e., ceasing to be rolled or bounced along the bottom of a body of water or ground surface (e.g., in a desert or erg). Finally, once it has accumulated, the sand becomes sandstone when it is compacted by pressure of overlying deposits and cemented by the precipitation of minerals within the pore spaces between sand grains.
The most common cementing materials are silica and calcium carbonate, which are often derived either from dissolution or from alteration of the sand after it was buried. Colors will usually be tan or yellow (from a blend of the clear quartz with the dark amber feldspar content of the sand). A predominant additional colorant in the southwestern United States is iron oxide, which imparts reddish tints ranging from pink to dark red (terracotta), with additional manganese imparting a purplish hue. Red sandstones are also seen in the Southwest and West of Britain, as well as central Europe and Mongolia. The regularity of the latter favors use as a source for masonry, either as a primary building material or as a facing stone, over other construction.
The environment where it is deposited is crucial in determining the characteristics of the resulting sandstone, which, in finer detail, include its grain size, sorting, and composition and, in more general detail, include the rock geometry and sedimentary structures. Principal environments of deposition may be split between terrestrial and marine, as illustrated by the following broad groupings:
Framework grains are silicate grains that are detrital in origin, their purpose is to support the sand. Framework grains range in size from 1/16 to 2 mm. These grains can then be classified into three different categories based on their mineral composition.
Matrix is very fine material, which is present within interstitial pore space between the framework grains. The interstitial pore space can be classified into two different varieties. One is to call the sandstone an arenite, and the other is to call it a wacke. Below is a definition of the differences between the two matrices.
Cement is what binds the siliclastic framework grains together. Cement is a secondary mineral that forms after deposition and during burial of the sandstone. These cementing materials may be either silicate minerals or non-silicate minerals, such as calcite.
Pore space includes the open spaces within a rock or a soil. The pore space in a rock has a direct relationship to the porosity and permeability of the rock. The porosity and permeability are directly influenced by the way the sand grains are packed together.
All sandstone are composed of the same general minerals. These minerals make up the framework components of the sandstones. Such components are quartz, feldspars, and lithic fragments. Matrix may also be present in the interstitial spaces between the framework grains. Below is a list of several major groups of sandstones. These groups are divided based on mineralogy and texture. Even though sandstones have very simple compositions which are based on framework grains, geologists have not been able to agree on a specific, right way, to classify sandstones. Sandstone classifications are typically done by point-counting a thin section using a method like the Gazzi-Dickinson Method. The composition of a sandstone can have important information regarding the genesis of the sediment when use with a triangle Quartz, Feldspar, Lithic Fragment (QFL diagrams). Many geologist however do not agree on how to separate the triangle parts into the single components so that the framework grains can be plotted. Therefore, there have been many published ways to classify sandstones, all of which are similar in their general format.
Visual aids are diagrams that allow geologists to interpret different characteristics about a sandstone. The following QFL chart and the sandstone provenance model correspond with each other therefore, when the QFL chart is plotted those points can the be plotted on the sandstone provenance model. The stage of textural maturity chart illustrates the different stages that a sandstone goes through.
Dott's (1964) sandstone classification scheme is one of many classification scheme used by geologists for classifying sandstones. Dott's scheme is a modification of Gilbert's classification of silicate sandstones, and it incorporates R.L. Folk's dual textural and compositional maturity concepts into one classification system. The philosophy behind combining Gilbert's classification scheme and R. L. Folk's classification scheme is that it is better able to "portray the continuous nature of textural variation from mudstone to arenite and from stable to unstable grain composition". Dott's classification scheme is based on the mineralogy of framework grains, and on the type of matrix present in between the framework grains.
In this specific classification scheme, Dott has set the boundary between arenite and wackes at 15% matrix. In addition to setting a boundary for what the matrix is, Dott also breaks up the different types framework grains that can be present in a sandstone into three major categories: quartz, feldspar, and lithic grains.
Arenites describe sandstone that have less than 15% clay matrix in between the framework grains.
Wacke describes sandstones that contain more than 15% clay matrix in between framework grains.
Arkose sandstones are more than 25 percent feldspar. The grains tend to be poorly rounded and less well sorted than those of pure quartz sandstones. These feldspar-rich sandstones come from rapidly eroding granitic and metamorphic terrains where chemical weathering is subordinate to physical weathering.
Graywacke sandstones are a heterogeneous mixture of lithic fragments and angular grains of quartz and feldspar, and/or grains surrounded by a fine-grained clay matrix. Much of this matrix is formed by relatively soft fragments, such as shale and some volcanic rocks, that are chemically altered and physically compacted after deep burial of the sandstone formation.
Aeolianite is a term used for a rock which is composed of sand grains that show signs of significant transportation by wind. These have usually been deposited in desert environments. They are commonly extremely well sorted and rich in quartz.
Oolite is more a limestone than a sandstone, but is made of sand-sized carbonate ooids, and is common in saline beaches with gentle wave action.
|Wikimedia Commons has media related to: Sandstone|
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