Limestone
A species of Sedimentary, Also known as Travertine Scientific name : Limestone RockType : Sedimentary
Limestone, A species of Sedimentary
Also known as:
Travertine
Scientific name: Limestone
RockType: Sedimentary
Description
Limestone is a famous and widespread sedimentary rock that is composed mainly of calcium carbonate crystals. Many iconic geologic formations, including the White Cliffs of Dover, Bryce Canyon of Utah, and Mammoth Cave of Kentucky, were formed primarily through the erosion patterns of this relatively soft stone. Limestone is utilized in roads and buildings, is key component in concrete, and a part of household products ranging from dyes to toothpaste.
Physical Properties
Colors
Yellow, white, gray
Texture
NonClastic
Chemical Properties
People often ask
General Info
How to Select
The desirability of limestone, a sedimentary rock, can depend on various factors:
1.Purity: High-calcium limestone (calcite > 95%) is often more valuable as it's integral in the production of cement, quicklime, and other industrial applications.
2.Color: While limestone can range from white to gray to tan to pink depending on its mineral content, particular colors may be more desirable depending on its intended use. For example, white or light-colored limestone is often used in building and decorative applications.
3.Texture and Grain Size: Fine-grained, smooth limestone is usually preferred for aesthetic and architectural uses.
4.Fossil Content: limestone that contains visible fossils can be especially desirable for educational purposes or for use as decorative stone.
5.Hardness and Durability: Dense, hard limestone is more desirable for construction uses as it's more durable and resistant to weathering.
6.Varieties: Certain types of limestone are particularly prized. For example, Coquina (a type of limestone composed mostly of seashells), Travertine (used extensively in the Roman Colosseum), Bamboo Jasper, and Pisolitic limestone each have unique properties making them desirable for specific purposes.
Remember, the most desirable qualities or varieties of limestone largely depend on its intended use and the preferences of the individual user or buyer.
Usage
Composition
Like most other sedimentary rocks, most limestone is composed of grains. Most grains in limestone are skeletal fragments of marine organisms such as coral or foraminifera. These organisms secrete shells made of aragonite or calcite, and leave these shells behind when they die. Other carbonate grains composing limestones are ooids, peloids, intraclasts, and extraclasts. Limestone often contains variable amounts of silica in the form of chert (chalcedony, flint, jasper, etc.) or siliceous skeletal fragment (sponge spicules, diatoms, radiolarians), and travertine (a precipitate of calcite and aragonite). 
Formation
The solubility of calcium carbonate (CaCO3) is controlled largely by the partial pressure of carbon dioxide (CO2) in the water. This is summarized in the reaction:
CaCO3 + H2O + CO2 → Ca2+(aq) + 2 HCO3−
Increases in temperature or decreases in pressure tend to reduce the partial pressure of CO2 and precipitate CaCO3. Reduction in salinity also reduces the solubility of CaCO3, by several orders of magnitude for fresh water versus seawater.
Near-surface water of the earth's oceans are oversaturated with CaCO3 by a factor of more than six. The failure of CaCO3 to precipitate out of these waters is likely due to interference by dissolved magnesium ions with nucleation of calcite crystals, the necessary first step in precipitation. Although ooids may form through purely inorganic processes, the bulk of CaCO3 precipitation in the oceans is the result of biological activity. Much of this takes place on carbonate platforms.
Types
Robert J. Dunham published his system for limestone in 1962. It focuses on the depositional fabric of carbonate rocks. Dunham divides the rocks into four main groups based on relative proportions of coarser clastic particles, based on criteria such as whether the grains were originally in mutual contact, and therefore self-supporting, or whether the rock is characterized by the presence of frame builders and algal mats.
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