Rimstone

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Rimstone - Endless Caverns, VA Rimstone - Endless Caverns, VA.jpg
Rimstone - Endless Caverns, VA
Rimstone in Cate's Cave, Anguilla RimestoneCaveFormation.JPG
Rimstone in Cate's Cave, Anguilla

Rimstone, also called gours, is a type of speleothem (cave formation) in the form of a stone dam. Rimstone is made up of calcite and other minerals that build up in cave pools. The formation created, which looks like stairs, often extends into flowstone above or below the original rimstone. Often, rimstone is covered with small, micro-gours on horizontal surfaces. Rimstone basins may form terraces that extend over hundreds of feet, with single basins known up to 200 feet long from Tham Xe Biang Fai in Laos. [1]

Contents

Formation

Rimstone dams form where there is some gradient, and hence flow, over the edge of a pool. Crystallization begins to occur at the air/water/rock interface. The turbulence caused by flow over the edge of the building dam may contribute to the outgassing or loss of carbon dioxide from water, and result in precipitation of mineral on this edge.

When dams form under running water, they tend to be higher when the passage is steeper. Shallow-gradient dams tend to be lower and more sinuous in nature. Rimstone is one of the most common cave formations, after flowstone, stalactites, and stalagmites.

Concrete derived micro-gours

Calthemite gours on a small rounded stalagmite - a secondary deposit derived from concrete Calthemite gours on a small rounded stalagmite - a secondary deposit derived from concrete.jpg
Calthemite gours on a small rounded stalagmite - a secondary deposit derived from concrete

Rimstone or gours can be formed by the secondary deposits derived from concrete, lime or mortar. These secondary deposits consisting primarily of calcium carbonate, are called calthemites and mimics the shapes and forms of cave speleothems to create stalactites, stalagmites, flowstone and gours. [2] Gours form beneath concrete structures on a floor with a gradual sloping surface or on the side of rounded stalagmites derived from concrete. Most of the calcium carbonate carried by the leachate is deposited as stalactites (when the drop rate is slower than one drop per minute), [2] leaving little in solution to be carried to the ground to create stalagmites, flowstone and gours. The leachate which does reach the ground usually evaporates quickly due to air movement beneath the concrete structure, hence micro-gours are more common.

The secondary deposits derived from concrete are the result of concrete degradation, where calcium ions are leached out of the concrete in solution and redeposited on the underside of a concrete structure. [2] Calcium carbonate deposition as micro-gours occur when the solution drops to the ground under the concrete structure. Carbon dioxide is absorbed into the alkaline leachate solution, [3] which facilitates the chemical reactions to precipitate any calcium carbonate remaining in solution as a stalagmite and micro-gours. This chemical reaction creating calthemites, is different from that which creates speleothems in limestone caves.

Secondary deposits, which create stalagmites, stalactites, flowstone, rimstone etc., outside the natural cave environment, are referred to as “calthemites”. [2] These concrete derived secondary deposits cannot be referred to as “speleothems” due to the definition of the word. [4] [5]

Related Research Articles

Stalactite

A stalactite is a mineral formation that hangs from the ceiling of caves, hot springs, or man-made structures such as bridges and mines. Any material that is soluble and that can be deposited as a colloid, or is in suspension, or is capable of being melted, may form a stalactite. Stalactites may be composed of lava, minerals, mud, peat, pitch, sand, sinter, and amberat. A stalactite is not necessarily a speleothem, though speleothems are the most common form of stalactite because of the abundance of limestone caves.

Stalagmite Elongate mineral formation found on a cave floor

A stalagmite is a type of rock formation that rises from the floor of a cave due to the accumulation of material deposited on the floor from ceiling drippings. Stalagmites are typically composed of calcium carbonate, but may consist of lava, mud, peat, pitch, sand, sinter and amberat.

Travertine Form of limestone deposited by mineral springs

Travertine is a form of limestone deposited by mineral springs, especially hot springs. Travertine often has a fibrous or concentric appearance and exists in white, tan, cream-colored, and even rusty varieties. It is formed by a process of rapid precipitation of calcium carbonate, often at the mouth of a hot spring or in a limestone cave. In the latter, it can form stalactites, stalagmites, and other speleothems. It is frequently used in Italy and elsewhere as a building material.

Speleothem Structure formed in a cave by the deposition of minerals from water

A speleothem is a geological formation by mineral deposits that accumulate over time in natural caves. Speleothems most commonly form in calcareous caves due to carbonate dissolution reactions. They can take a variety of forms, depending on their depositional history and environment. Their chemical composition, gradual growth, and preservation in caves make them useful paleoclimatic proxies.

Soda straw

A soda straw is a speleothem in the form of a hollow mineral cylindrical tube. They are also known as tubular stalactites. Soda straws grow in places where water leaches slowly through cracks in rock, such as on the roofs of caves. Soda straws in caves rarely grow more than a few millimetres per year and may average one tenth of a millimetre per year. A soda straw can turn into a stalactite if the hole at the bottom is blocked, or if the water begins flowing on the outside surface of the hollow tube. Soda straws can also form outside the cave environment on exposed concrete surfaces as a type of calthemite, growing significantly faster than those formed on rock.

Luray Caverns

Luray Caverns, originally called Luray Cave, is a cave just west of Luray, Virginia, United States, which has drawn many visitors since its discovery in 1878. The cavern system is generously adorned with speleothems such as columns, mud flows, stalactites, stalagmites, flowstone, and mirrored pools. The caverns are perhaps best known for the Great Stalacpipe Organ, a lithophone made from solenoid-fired strikers that tap stalactites of various sizes to produce tones similar to those of xylophones, tuning forks, or bells.

Jewel Cave National Monument

Jewel Cave National Monument contains Jewel Cave, currently the third longest cave in the world, with 200.3 miles of mapped passageways. It is located approximately 13 miles (21 km) west of the town of Custer in Black Hills of South Dakota. It became a national monument in 1908.

Dolomite (rock) Sedimentary carbonate rock that contains a high percentage of the mineral dolomite

Dolomite (also known as dolomite rock, dolostone or dolomitic rock) is a sedimentary carbonate rock that contains a high percentage of the mineral dolomite, CaMg(CO3)2. In old USGS publications, it was referred to as magnesian limestone, a term now reserved for magnesium-deficient dolomites or magnesium-rich limestones. Dolomite has a stoichiometric ratio of nearly equal amounts of magnesium and calcium. Most dolomite rock formed as a magnesium replacement of limestone or lime mud before lithification. Dolomite rock is resistant to erosion and can either contain bedded layers or be unbedded. It is less soluble than limestone in weakly acidic groundwater, but it can still develop solution features (karst) over time. Dolomite rock can act as an oil and natural gas reservoir.

Flowstone

Flowstones are composed of sheetlike deposits of calcite or other carbonate minerals, formed where water flows down the walls or along the floors of a cave. They are typically found in "solution caves", in limestone, where they are the most common speleothem. However, they may form in any type of cave where water enters that has picked up dissolved minerals. Flowstones are formed via the degassing of vadose percolation waters.

Efflorescence

In chemistry, efflorescence is the migration of a salt to the surface of a porous material, where it forms a coating. The essential process involves the dissolving of an internally held salt in water, or occasionally in another solvent. The water, with the salt now held in solution, migrates to the surface, then evaporates, leaving a coating of the salt.

Cave popcorn Small nodes of calcite, aragonite or gypsum that form on surfaces in caves

Cave popcorn, or coralloids, are small nodes of calcite, aragonite or gypsum that form on surfaces in caves, especially limestone caves. They are a common type of speleothem.

Cave of the Mounds

Cave of the Mounds, a natural limestone cave located near Blue Mounds, Wisconsin, United States, is named for two nearby hills called the Blue Mounds. It is located in the southern slope of the east hill. The cave's beauty comes from its many varieties of mineral formations called speleothems. The Chicago Academy of Sciences considers the Cave of the Mounds to be "the significant cave of the upper Midwest" because of its beauty, and it is promoted as the "jewel box" of major American caves. In 1987, the United States Department of the Interior and the National Park Service designated the cave as a National Natural Landmark.

Anthodite

Anthodites (Greek ἄνθος ánthos, "flower", -ode, adjectival combining form, -ite adjectival suffix) are speleothems (cave formations) composed of long needle-like crystals situated in clusters which radiate outward from a common base. The "needles" may be quill-like or feathery. Most anthodites are made of the mineral aragonite (a variety of calcium carbonate, CaCO3), although some are composed of gypsum (CaSO4·2H2O).

Pettyjohn Cave Cave in Georgia (US)

Pettyjohn Cave is a karst cave located in Walker County, Georgia on the east side Pigeon Mountain in the Appalachian Plateau of Northwest Georgia. It has a surveyed length of 31,490 ft and reaches a depth of 235 ft. The cave is accessible via a path from a gravel parking area on the side of Rocky Lane. Out of the 242 listed, it is 119th longest cave in the United States as declared by the Georgia Speleological Survey.

Castellana Caves

The Castellana Caves are a karst cave system located in the municipality of Castellana Grotte, in the Metropolitan City of Bari, Apulia, southern Italy.

Solutional cave

A solutional cave, solution cave, or karst cave is a cave usually formed in the soluble rock limestone. It is the most frequently occurring type of cave. It can also form in other rocks, including chalk, dolomite, marble, salt beds, and gypsum.

Concrete degradation Damages inflicted to concrete by various harmful physical phenomena and chemical or biological processes

Concrete degradation may have various causes. Concrete can be damaged by fire, aggregate expansion, sea water effects, bacterial corrosion, calcium leaching, physical damage and chemical damage. This process adversely affects concrete exposed to these damaging stimuli.

Calcite rafts Cave-crystallized calcite crusts

Calcite crystals form on the surface of quiescent bodies of water, even when the bulk water is not supersaturated with respect to calcium carbonate. The crystals grow, attach to one other and appear to be floating rafts of a white, opaque material. The floating materials have been referred to as calcite rafts or "leopard spots".

Cliefden Caves Protected area in New South Wales, Australia

The Cliefden Caves ia heritage-listed geoheritage site in Mandurama, Cowra Shire, New South Wales, Australia. The caves comprises Ordovician fossil localities, limestone caves, a spring and tufa dams, and a site where limestone was first discovered in inland Australia.

Calthemite Secondary calcium carbonate deposit growing under man-made structures

Calthemite is a secondary deposit, derived from concrete, lime, mortar or other calcareous material outside the cave environment. Calthemites grow on or under, man-made structures and mimic the shapes and forms of cave speleothems, such as stalactites, stalagmites, flowstone etc. Calthemite is derived from the Latin calx "lime" + Latin < Greek théma, "deposit" meaning ‘something laid down’, and the Latin –ita < Greek -itēs – used as a suffix indicating a mineral or rock. The term "speleothem", due to its definition can only be used to describe secondary deposits in caves and does not include secondary deposits outside the cave environment.

References

  1. Dave Bunnell. "The World's Largest Cave Formations". The Virtual Cave. Retrieved December 16, 2008.
  2. 1 2 3 4 Smith, G K. (2016). "Calcite straw stalactites growing from concrete structures". Cave and Karst Science 43(1), pp4-10.
  3. Macleod, G, Hall, A J and Fallick, A E, 1990. An applied mineralogical investigation of concrete degradation in a major concrete road bridge. Mineralogical Magazine, Vol.54, 637–644.
  4. Hill, C A and Forti, P, (1997). Cave Minerals of the World, Second Edition. [Huntsville, Alabama: National Speleological Society Inc.] ISBN   1-879961-07-5
  5. Moore, G W. (1952). "Speleothems – a new cave term". National Speleological Society News, Vol.10(6), p.2.

Sources