At this location, and many other locations, the Kaibab Limestone is fossiliferous and dolomitic. Photograph by the United States Geological Survey. Dolomitic limestone is a rock composed mainly of calcite, but some of that calcite has been altered to dolomite. Dolomite is thought to form when the calcite CaCO 3 in carbonate sediments or in limestone is modified by magnesium-rich groundwater.
The available magnesium facilitates the conversion of calcite into dolomite CaMg CO 3 2. This chemical change is known as "dolomitization. Dolomitization can completely alter a limestone into a dolomite, or it can partially alter the rock to form a "dolomitic limestone.
Fossiliferous Limestone: Ammonite fossils found in limestone quarry in Germany. Ammonite fossils are abundant in the area around Nuremberg and Stuttgart. Fossiliferous limestone is a limestone that contains obvious and abundant fossils. They are usually marine invertebrates such as brachiopods, crinoids, mollusks, gastropods, and coral. These are the normal shell and skeletal fossils found in many types of limestone. Fossiliferous limestone often contains information about the environment of deposition, and where the organisms lived or were deposited.
Paleontologists can often examine the fossils and determine the geologic age of the rock. Lithographic Limestone: In , workers at NOAA's printing shop ink a slab of lithographic limestone that contains an image of a nautical chart.
In , NOAA produced approximately , lithographic prints using this method. A crop from an image in the NOAA archive. Lithographic limestone is a dense rock with a very fine and very uniform grain size.
It occurs in thin beds which separate easily to form a very smooth surface. In the late s, a printing process known as lithography named after the stones used was developed to reproduce images by drawing them on the stone with an oil-based ink, then using that stone to press multiple copies of the image. Lithographic printing developed into an art form that produced many of the finest maps, navigational charts, posters, and bookplates of the 18th and 19th century.
Printing with large stones weighing hundreds of pounds to over one ton was cumbersome work. Eventually lithographic printing was done using high-speed presses in which the image was inked on metal rollers and transferred onto sheets or rolls of paper as they streamed through the press.
Oolitic Limestone: A specimen of limestone composed almost entirely of oolites. Photograph by James St. John, displayed here under a Creative Commons attribution license. Oolites or ooliths are small, sand-size clasts of calcium carbonate with a spherical to ovate shape.
They form by the concentric accumulation of calcium carbonate layers around a nucleus that might be a sand grain, a shell fragment, a coral fragment, or a particle of fecal debris. They are thought to form by inorganic precipitation of material around a nucleus while the clast is transported in wave-agitated waters or rolling across sediment surfaces.
In some parts of the Bahamas Platform, oolites are one of the most abundant clasts found in the sediment. In areas where currents from deep water ascend onto the platform, broad areas are covered by great thicknesses of sediment that is almost entirely oolitic. Oolitic limestone is found in many parts of the world. Oolitic sediment is found in Great Salt Lake, Utah. Some sedimentary rocks are composed almost entirely of ooids and the calcium carbonate cement that binds them together.
Travertine used as flooring tile and wall panels in a modern home interior. Travertine is a variety of limestone that forms where geothermally heated alkaline water, supercharged with dissolved gases and minerals, emerges at the surface. There, calcium carbonate and other minerals precipitate as the water degases and begins to evaporate. Travertine can also form where these waters emerge into subsurface caverns. There, it can precipitate as cave formations such as stalactites, stalagmites, and flowstone.
When pure, travertine is white, but it is often stained by the presence of other minerals to cream, tan, greenish, brownish, and other colors. Because the precipitation is rapid and forms as encrustations on younger materials, travertine is often a banded rock with numerous voids and cavities. It sometimes contains inclusions of organic and mineral debris from the cave or surface environment. Travertine was mined and used as an architectural stone in ancient Egypt and ancient Rome.
Today, Egypt and Italy are famous sources of travertine that is exported throughout the world. It is sawn or sheared into floor tiles, window sills, wall panels, stair treads, and other shapes, mainly for interior use.
High-quality material can sometimes accept a polish. The material can be recognized by its low hardness 3 on the Mohs scale , banded appearance, and porous texture. Tufa is a porous rock that forms from the precipitation of calcium carbonate, often at a hot spring or along the shoreline of an alkaline lake where waters are saturated with calcium carbonate.
Tufa is a porous limestone produced by precipitation of calcium carbonate from the waters of a hot spring or other body of surface water that has the ability to precipitate volumes of calcium carbonate. The pore space in tufa often results when plant material is trapped in precipitating calcium carbonate. One of the most famous locations where tufa is actively forming is at Mono Lake, Yosemite National Park.
The most spectacular tufa features at the lake are known as "tufa towers". They form by the interaction of freshwater springs and alkaline lake water. In spite of its gnarly appearance as a rock, tufa actually has numerous architectural uses. When found in thick accumulations, tufa can be mined and sawn into blocks and sheets just like any other dimension stone.
It produces a stone with a very rugged appearance. Crushed Limestone: The Unsung Mineral Hero: Crushed stone is often looked upon as one of the lowliest of commodities; however, it is used for such a wide variety of purposes in so many industries that it should be elevated to a position of distinction.
It is the geologic commodity upon which almost everything is built. The Wordle word cloud above shows just a few of its many diverse uses. Tectonic Association Carbonates of all types are commonly associated with regions of tectonic stability and tropical climates, that is no mountain building, and stable, shallow water environments associated with continental shelves or epeiric epicontinental seas.
Go to Carbonate Tectonics for more explanation. It was a high energy environment as indicated by the lack of fine grained sediment micrite , and the presence of spar cement. Spar is crystalline calcite crystals precipitated by ground water in the spaces between the fossils after deposition. Before this became a rock we can imagine it as a rubble pile of skeletons lying on the bottom with no other sediment intermixed with them.
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