Oolite
Overview
 
Oolite is a sedimentary rock
Sedimentary rock
Sedimentary rock are types of rock that are formed by the deposition of material at the Earth's surface and within bodies of water. Sedimentation is the collective name for processes that cause mineral and/or organic particles to settle and accumulate or minerals to precipitate from a solution....

 formed from ooids, spherical grains composed of concentric layers. The name derives from the Hellenic
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...

 word òoion for egg
Egg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...

. Strictly, oolites consist of ooids of diameter 0.25–2 mm; rocks
Rock (geology)
In geology, rock or stone is a naturally occurring solid aggregate of minerals and/or mineraloids.The Earth's outer solid layer, the lithosphere, is made of rock. In general rocks are of three types, namely, igneous, sedimentary, and metamorphic...

 composed of ooids larger than 2 mm are called pisolite
Pisolite
A pisolite is a sedimentary rock made of pisoids, which are concretionary grains - often of calcium carbonate, but sometimes of rarer minerals - which resemble ooids but are always more than 2 mm in diameter. These grains are approximately spherical and have concentric layers reaching...

s. The term oolith can refer to oolite or individual ooids.
Ooids are most commonly composed of calcium carbonate
Calcium carbonate
Calcium carbonate is a chemical compound with the formula CaCO3. It is a common substance found in rocks in all parts of the world, and is the main component of shells of marine organisms, snails, coal balls, pearls, and eggshells. Calcium carbonate is the active ingredient in agricultural lime,...

 (calcite
Calcite
Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate . The other polymorphs are the minerals aragonite and vaterite. Aragonite will change to calcite at 380-470°C, and vaterite is even less stable.-Properties:...

 or aragonite
Aragonite
Aragonite is a carbonate mineral, one of the two common, naturally occurring, crystal forms of calcium carbonate, CaCO3...

), but can be composed of phosphate, chert
Chert
Chert is a fine-grained silica-rich microcrystalline, cryptocrystalline or microfibrous sedimentary rock that may contain small fossils. It varies greatly in color , but most often manifests as gray, brown, grayish brown and light green to rusty red; its color is an expression of trace elements...

, dolomite
Dolomite
Dolomite is a carbonate mineral composed of calcium magnesium carbonate CaMg2. The term is also used to describe the sedimentary carbonate rock dolostone....

 or iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...

 minerals, including hematite
Hematite
Hematite, also spelled as haematite, is the mineral form of iron oxide , one of several iron oxides. Hematite crystallizes in the rhombohedral system, and it has the same crystal structure as ilmenite and corundum...

.
Encyclopedia
Oolite is a sedimentary rock
Sedimentary rock
Sedimentary rock are types of rock that are formed by the deposition of material at the Earth's surface and within bodies of water. Sedimentation is the collective name for processes that cause mineral and/or organic particles to settle and accumulate or minerals to precipitate from a solution....

 formed from ooids, spherical grains composed of concentric layers. The name derives from the Hellenic
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...

 word òoion for egg
Egg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...

. Strictly, oolites consist of ooids of diameter 0.25–2 mm; rocks
Rock (geology)
In geology, rock or stone is a naturally occurring solid aggregate of minerals and/or mineraloids.The Earth's outer solid layer, the lithosphere, is made of rock. In general rocks are of three types, namely, igneous, sedimentary, and metamorphic...

 composed of ooids larger than 2 mm are called pisolite
Pisolite
A pisolite is a sedimentary rock made of pisoids, which are concretionary grains - often of calcium carbonate, but sometimes of rarer minerals - which resemble ooids but are always more than 2 mm in diameter. These grains are approximately spherical and have concentric layers reaching...

s. The term oolith can refer to oolite or individual ooids.

Composition

Ooids are most commonly composed of calcium carbonate
Calcium carbonate
Calcium carbonate is a chemical compound with the formula CaCO3. It is a common substance found in rocks in all parts of the world, and is the main component of shells of marine organisms, snails, coal balls, pearls, and eggshells. Calcium carbonate is the active ingredient in agricultural lime,...

 (calcite
Calcite
Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate . The other polymorphs are the minerals aragonite and vaterite. Aragonite will change to calcite at 380-470°C, and vaterite is even less stable.-Properties:...

 or aragonite
Aragonite
Aragonite is a carbonate mineral, one of the two common, naturally occurring, crystal forms of calcium carbonate, CaCO3...

), but can be composed of phosphate, chert
Chert
Chert is a fine-grained silica-rich microcrystalline, cryptocrystalline or microfibrous sedimentary rock that may contain small fossils. It varies greatly in color , but most often manifests as gray, brown, grayish brown and light green to rusty red; its color is an expression of trace elements...

, dolomite
Dolomite
Dolomite is a carbonate mineral composed of calcium magnesium carbonate CaMg2. The term is also used to describe the sedimentary carbonate rock dolostone....

 or iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...

 minerals, including hematite
Hematite
Hematite, also spelled as haematite, is the mineral form of iron oxide , one of several iron oxides. Hematite crystallizes in the rhombohedral system, and it has the same crystal structure as ilmenite and corundum...

. Dolomitic and chert ooids are most likely the result of the replacement of the original texture in limestone. Oolitic hematite occurs at Red Mountain
Red Mountain, Birmingham, Alabama
Red Mountain is a long ridge running southwest-northeast and dividing Jones Valley from Shades Valley south of Birmingham, Alabama. It is part of the Ridge-and-Valley region of the Appalachian mountains...

 near Birmingham, Alabama
Birmingham, Alabama
Birmingham is the largest city in Alabama. The city is the county seat of Jefferson County. According to the 2010 United States Census, Birmingham had a population of 212,237. The Birmingham-Hoover Metropolitan Area, in estimate by the U.S...

, along with oolitic limestone.

They are usually formed in warm, supersaturated, shallow, highly agitated marine water intertidal environments,though some are formed in inland lakes. The mechanism of formation starts with a small fragment of sediment acting as a 'seed' ,e.g. a piece of a shell. Strong intertidal currents wash the 'seeds' around on the seabed where they accumulate layers of chemically precipitated calcite from the supersaturated water.The oolites are commonly found in large current bedding structures that resemble sanddunes. The size of the oolite reflects the time they have had exposed to the water before they were covered with later sediment.

Oolites are often used in the home aquarium industry because their small grain size (0.2 to 1.22 mm) is ideal for shallow static beds and bottom covering of up to 1" in depth. Also known as "oolitic" sand, the sugar-sized round grains of this sand pass easily through the gills of gobies
Goby
The gobies form the family Gobiidae, which is one of the largest families of fish, with more than 2,000 species in more than 200 genera. Most are relatively small, typically less than 10 cm in length...

 and other sand-sifting organisms. Importantly, this incredibly smooth sand promotes the growth of bacteria, which are important biofilters in home aquaria. Because of its extremely small grain size, oolitic sand has a lot of surface area, which promotes high bacterial growth.

Occurrence

Some exemplar oolitic limestone
Limestone
Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....

, a common term for an oolite, was formed in England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...

 during the Jurassic
Jurassic
The Jurassic is a geologic period and system that extends from about Mya to  Mya, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the age of reptiles. The start of the period is marked by...

 period, and forms the Cotswold Hills, the Isle of Portland
Isle of Portland
The Isle of Portland is a limestone tied island, long by wide, in the English Channel. Portland is south of the resort of Weymouth, forming the southernmost point of the county of Dorset, England. A tombolo over which runs the A354 road connects it to Chesil Beach and the mainland. Portland and...

 with its famous Portland Stone, and part of the North Yorkshire Moors
North York Moors
The North York Moors is a national park in North Yorkshire, England. The moors are one of the largest expanses of heather moorland in the United Kingdom. It covers an area of , and it has a population of about 25,000...

. A particular type, Bath Stone
Bath Stone
Bath Stone is an Oolitic Limestone comprising granular fragments of calcium carbonate. Originally obtained from the Combe Down and Bathampton Down Mines under Combe Down, Somerset, England, its warm, honey colouring gives the World Heritage City of Bath, England its distinctive appearance...

, gives the buildings of the World Heritage City of Bath their distinctive appearance.

The islands of the Lower Keys in the Florida Keys
Florida Keys
The Florida Keys are a coral archipelago in southeast United States. They begin at the southeastern tip of the Florida peninsula, about south of Miami, and extend in a gentle arc south-southwest and then westward to Key West, the westernmost of the inhabited islands, and on to the uninhabited Dry...

, as well as some barrier islands east of Miami bordering Biscayne Bay
Biscayne Bay
Biscayne Bay is a lagoon that is approximately 35 miles long and up to 8 miles wide located on the Atlantic coast of South Florida, United States. It is usually divided for purposes of discussion and analysis into three parts: North Bay, Central Bay, and South Bay. Its area is...

, are mainly oolitic limestone, which was formed by deposition when shallow seas covered the area between periods of glaciation
Glacial period
A glacial period is an interval of time within an ice age that is marked by colder temperatures and glacier advances. Interglacials, on the other hand, are periods of warmer climate within an ice age...

. The material consolidated and eroded during later exposure above the ocean surface.

One of the world's largest freshwater lakebed oolites is the Shoofly Oolite, a section of the Glenns Ferry Formation on southwestern Idaho
Idaho
Idaho is a state in the Rocky Mountain area of the United States. The state's largest city and capital is Boise. Residents are called "Idahoans". Idaho was admitted to the Union on July 3, 1890, as the 43rd state....

's Snake River Plain
Snake River Plain
The Snake River Plain is a geologic feature located primarily within the state of Idaho in the United States of America. It stretches about westward from northwest of the state of Wyoming to the Idaho-Oregon border. The plain is a wide flat bow-shaped depression, and covers about a quarter of Idaho...

. 10 million years ago, the Plain formed the bed of Lake Idaho. Wave action in the lake washed sediments back and forth in the shallows on the southwestern shore, forming ooids and depositing them on steeper benches near the shore in 2- to 40-feet thicknesses. When the lake drained (2 to 4 million years ago), the oolite was left behind, along with siltstone
Siltstone
Siltstone is a sedimentary rock which has a grain size in the silt range, finer than sandstone and coarser than claystones.- Description :As its name implies, it is primarily composed of silt sized particles, defined as grains 1/16 - 1/256 mm or 4 to 8 on the Krumbein phi scale...

, volcanic tuff
Tuff
Tuff is a type of rock consisting of consolidated volcanic ash ejected from vents during a volcanic eruption. Tuff is sometimes called tufa, particularly when used as construction material, although tufa also refers to a quite different rock. Rock that contains greater than 50% tuff is considered...

s and alluvium from adjacent mountain slopes. The other sediments eroded away, while the more resistant oolite weathered into hummocks, small arches and other intriguing natural "sculptures." The Shoofly Oolite lies on public land west of Bruneau, Idaho
Bruneau, Idaho
Bruneau is an unincorporated community in Owyhee County in the southwestern part of the U.S. state of Idaho. Located at , the community sits at an altitude of 2549 feet ....

 managed by the Bureau of Land Management
Bureau of Land Management
The Bureau of Land Management is an agency within the United States Department of the Interior which administers America's public lands, totaling approximately , or one-eighth of the landmass of the country. The BLM also manages of subsurface mineral estate underlying federal, state and private...

 (BLM). The physical and chemical properties of the Shoofly Oolite are the setting for a suite of rare plants, which the BLM protects through land use management and on-site interpretation.

This type of limestone is also found in Indiana
Indiana
Indiana is a US state, admitted to the United States as the 19th on December 11, 1816. It is located in the Midwestern United States and Great Lakes Region. With 6,483,802 residents, the state is ranked 15th in population and 16th in population density. Indiana is ranked 38th in land area and is...

 in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

. The town of Oolitic, Indiana
Oolitic, Indiana
Oolitic is a town in Indian Creek and Shawswick townships, Lawrence County, Indiana, United States. The population was 1,184 at the 2010 census.-Geography:Oolitic is located at ....

, was founded for the trade of limestone and bears its name. Quarries in Oolitic, Bedford
Bedford, Indiana
As of the census of 2000, there were 13,768 people, 6,054 households, and 3,644 families residing in the city. The population density was 1,157.1 people per square mile . There were 6,618 housing units at an average density of 556.2 per square mile...

, and Bloomington
Bloomington, Indiana
Bloomington is a city in and the county seat of Monroe County in the southern region of the U.S. state of Indiana. The population was 80,405 at the 2010 census....

 contributed the materials for such iconic U.S. landmarks as the Empire State Building
Empire State Building
The Empire State Building is a 102-story landmark skyscraper and American cultural icon in New York City at the intersection of Fifth Avenue and West 34th Street. It has a roof height of 1,250 feet , and with its antenna spire included, it stands a total of 1,454 ft high. Its name is derived...

 in New York and the Pentagon
The Pentagon
The Pentagon is the headquarters of the United States Department of Defense, located in Arlington County, Virginia. As a symbol of the U.S. military, "the Pentagon" is often used metonymically to refer to the Department of Defense rather than the building itself.Designed by the American architect...

 in Arlington, Virginia. Many of the buildings on the Indiana University
Indiana University Bloomington
Indiana University Bloomington is a public research university located in Bloomington, Indiana, in the United States. IU Bloomington is the flagship campus of the Indiana University system. Being the flagship campus, IU Bloomington is often referred to simply as IU or Indiana...

 campus in Bloomington are built with native oolitic limestone material, and the Soldiers' and Sailors' Monument
Soldiers' and Sailors' Monument (Indianapolis)
The Indiana Soldiers' and Sailors' Monument is a tall neoclassical monument in the center of Indianapolis, Indiana that was designed by German architect Bruno Schmitz and completed in 1901....

 in downtown Indianapolis
Indianapolis
Indianapolis is the capital of the U.S. state of Indiana, and the county seat of Marion County, Indiana. As of the 2010 United States Census, the city's population is 839,489. It is by far Indiana's largest city and, as of the 2010 U.S...

, Indiana, is built mainly of grey oolitic limestone. The 1979 movie Breaking Away
Breaking Away
Breaking Away is a 1979 American film. A coming of age story, it follows a group of four male teenagers in Bloomington, Indiana, who have recently graduated from high school. It stars Dennis Christopher, Dennis Quaid, Daniel Stern , Jackie Earle Haley, Barbara Barrie and Paul Dooley...

centers around the sons of quarry workers in Bloomington.

Oolites also appear in the Conococheague limestone
Conococheague Formation
The Conococheague Formation is a mapped Appalachian bedrock unit of Cambrian age, consisting primarily of limestone and dolomite. It occurs in central Maryland, southern and central Pennsylvania, northern Virginia and easternmost West Virginia....

, of Cambrian
Cambrian
The Cambrian is the first geological period of the Paleozoic Era, lasting from Mya ; it is succeeded by the Ordovician. Its subdivisions, and indeed its base, are somewhat in flux. The period was established by Adam Sedgwick, who named it after Cambria, the Latin name for Wales, where Britain's...

 age, in the Great Appalachian Valley
Great Appalachian Valley
The Great Valley, also called the Great Appalachian Valley or Great Valley Region, is one of the major landform features of eastern North America. It is a gigantic trough — a chain of valley lowlands — and the central feature of the Appalachian Mountain system...

 in Pennsylvania
Pennsylvania
The Commonwealth of Pennsylvania is a U.S. state that is located in the Northeastern and Mid-Atlantic regions of the United States. The state borders Delaware and Maryland to the south, West Virginia to the southwest, Ohio to the west, New York and Ontario, Canada, to the north, and New Jersey to...

, Maryland
Maryland
Maryland is a U.S. state located in the Mid Atlantic region of the United States, bordering Virginia, West Virginia, and the District of Columbia to its south and west; Pennsylvania to its north; and Delaware to its east...

, West Virginia
West Virginia
West Virginia is a state in the Appalachian and Southeastern regions of the United States, bordered by Virginia to the southeast, Kentucky to the southwest, Ohio to the northwest, Pennsylvania to the northeast and Maryland to the east...

, and Virginia
Virginia
The Commonwealth of Virginia , is a U.S. state on the Atlantic Coast of the Southern United States. Virginia is nicknamed the "Old Dominion" and sometimes the "Mother of Presidents" after the eight U.S. presidents born there...

.

Roggenstein is a term describing a specific type of oolite in which the cementing matter is argillaceous.

See also

  • Geologic timescale
  • Geology of Great Britain
  • Pearl
    Pearl
    A pearl is a hard object produced within the soft tissue of a living shelled mollusk. Just like the shell of a mollusk, a pearl is made up of calcium carbonate in minute crystalline form, which has been deposited in concentric layers. The ideal pearl is perfectly round and smooth, but many other...

    s: also formed from concentric layers of calcium carbonate
  • Oolitic aragonite sand
    Oolitic aragonite sand
    Oolitic aragonite sand forms in tropical waters. Most of the topography of the Bahama Banks is composed of calcium carbonate oolitic aragonite sand material....

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
x
OK