In geology, frostwork is a type of
speleothem with acicular ("needle-like") growths almost always composed of
aragonite
Aragonite is a carbonate mineral and one of the three most common naturally occurring crystal forms of calcium carbonate (), the others being calcite and vaterite. It is formed by biological and physical processes, including precipitation fr ...
(a
polymorph of calcite) or
calcite
Calcite is a Carbonate minerals, carbonate mineral and the most stable Polymorphism (materials science), polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on ...
replaced aragonite.
[Hill, C. and Forti, P. (1997), ''Cave Minerals of the World'', National Speleological Society, 2nd Edition.] It is a variety of
anthodite. Frostwork can also be made of
opal
Opal is a hydrated amorphous form of silicon dioxide, silica (SiO2ยท''n''H2O); its water content may range from 3% to 21% by weight, but is usually between 6% and 10%. Due to the amorphous (chemical) physical structure, it is classified as a ...
or
gypsum.
In some caves frostwork may grow on top of
cave popcorn or
boxwork.
Formation
The origin of frostwork is somewhat controversial. Formation of cave frostwork has been attributed to moist, circulating air which, containing dissolved
calcium carbonate, drifted against rock surfaces and coated them with the delicate crystals. Frostwork has also been attributed to water seepage from cave passageways in which there are relatively high
evaporation
Evaporation is a type of vaporization that occurs on the Interface (chemistry), surface of a liquid as it changes into the gas phase. A high concentration of the evaporating substance in the surrounding gas significantly slows down evapora ...
rates.
Occurrence
Notable frostwork deposits are found in a number of
cave
Caves or caverns are natural voids under the Earth's Planetary surface, surface. Caves often form by the weathering of rock and often extend deep underground. Exogene caves are smaller openings that extend a relatively short distance undergrou ...
s in the
Black Hills region of
South Dakota
South Dakota (; Sioux language, Sioux: , ) is a U.S. state, state in the West North Central states, North Central region of the United States. It is also part of the Great Plains. South Dakota is named after the Dakota people, Dakota Sioux ...
, US, most notable in
Wind Cave National Park and
Jewel Cave National Monument and
Timpanogos Cave in
Utah
Utah is a landlocked state in the Mountain states, Mountain West subregion of the Western United States. It is one of the Four Corners states, sharing a border with Arizona, Colorado, and New Mexico. It also borders Wyoming to the northea ...
. Perhaps the most extensive displays known are found in
Lechuguilla Cave,
New Mexico
New Mexico is a state in the Southwestern United States, Southwestern region of the United States. It is one of the Mountain States of the southern Rocky Mountains, sharing the Four Corners region with Utah, Colorado, and Arizona. It also ...
, US.
Gallery
File:Tropfsteine.svg, Diagram of dripstone cave structures (frostwork labelled AA)
File:Popcorn-with-Frostwork.jpg, Cave popcorn with frostwork
References
External links
Wind Cave National Park: Speleothems
Speleothems
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