Frostwork

In geology, frostwork is a type of speleothem (cave formation) with acicular ("needle-like") growths almost always composed of aragonite (a polymorph of calcite) or calcite replaced aragonite.[1] It is a variety of anthodite. Frostwork can also be made of opal or gypsum.[2] In some caves frostwork may grow on top of cave popcorn or boxwork.

frostwork
Frostwork in Jewel Cave, South Dakota.
Architectural "frost-work" in carved stone, on the Diana Fountain, London, c. 1690

In architecture frost-work or frostwork refers to a style of rustication carved with a vertically-oriented pattern evoking hanging pond-weed or algae, or icicles. It is mainly found in garden architecture, where water is to flow over or near the surface.[3] Other decorative arts may use the term for other decorative patterns imitating frost or ice.

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 rates.

Occurrence

Notable frostwork deposits are found in a number of caves in the Black Hills region of South Dakota, US, most notable in Wind Cave National Park and Jewel Cave National Monument and Timpanogos Cave in Utah. Perhaps the most extensive displays known are found in Lechuguilla Cave, New Mexico, US.

  • Diagram of dripstone cave structures (frostwork labelled AA)
    Diagram of dripstone cave structures (frostwork labelled AA)
  • Cave popcorn with frostwork
    Cave popcorn with frostwork

References
  1. Hill, C. and Forti, P. (1997), Cave Minerals of the World, National Speleological Society, 2nd Edition.
  2. KellerLynn, K. (2009). Wind Cave National Park Geologic Resources Inventory Report (PDF). Denver: National Park Service.
  3. Looking at buildings, "Rustication"


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