Cave Features

Slightly acidic groundwater in limestone regions gradually dissolves passages and caverns in the underground rock. Geologists call this karst topography.

Speleothems are cave features created after the underground chamber has been formed. They are a result of slow-moving water, usually containing calcium carbonate, which has been dissolved from the limestone where the cave was formed. When this water enters the cave, a chemical change causes the calcium carbonate to precipitate (harden), creating all manner of cave formations and features -- speleothems.

Calcite is the stable form of the widely distributed mineral calcium carbonate (CaCO3). Calcite is the primary mineral component of speleothems as well as limestone, the sedimentary rock in which most caves are formed.

Aragonite is also precipitated calcium carbonate, differing from calcite only by its internal crystalline structure. Aragonite crystals are long and needle-like (acicular), while calcite crystals are more stubby.

Travertine is a type of limestone deposited at the mouths of hot and cold calcareous springs. When it is porous, Tufa is the term used to describe such rock.


Speleothem Glossary

Dripstone: Calcium carbonate deposited from solution as water enters a cave through the zone of aeration. Forms stalactites, stalagmites and other cave deposits.

Bottlebrush: Formation of stalactites once immersed in a cave pool for a long period, during a change in the pool's waterflow.

Canopy: A type of flowstone that protrudes from a cave wall or speleothem and has a relatively flat surface underneath.

Baldacchino Canopy: An overhanging belly of calcite, formed where the surface of a cave pool has receded beneath a growing stalagmite or flowstone mound.

Bell Canopy: A mushroom-shaped speleothem, formed due to variations in the flowing water that forms the flowstone.

Clastic Canopy: Speleothem forming when flowstone flows over material such as rock or clay, that is washed away later.

Cave Pearl: A smooth, polished and rounded speleothem found in shallow hollows into which water drips.

Column: Calcite formation created by the union of stalagmites and stalactites.

Coral: Very small short stalks with bulbous ends, usually occurring in numbers in patches.

Curtain: A speleothem in the form of a wavy or folded sheet hanging from the roof or wall of a cave, often translucent and resonant.

Drapery: Deposits from calcite-rich solutions flowing along an overhung surface of a wall or sloping ceiling as it streams slowly downward.

Dripstone: Calcium carbonate deposited from solution as water enters a cave through the zone of aeration. Forms stalactites, stalagmites and other cave deposits.

Flowstone: General term for deposits formed by dripping and flowing water on walls and floors of caves.

Flowstone Falls: Sheets of calcite lining a vertical shaft.

Folia: A rare formation found near or just below the water line, probably from precipitates on water surfaces that accrete to walls.

Flower: Speleothem with crystal petals radiating from a central point ,usually composed of gypsum, epsomite or halite. Due to changes in flow rate, the flower petals tend to curve, much like helictites.

Helictite: Contorted depositional speleothem, formed from calcite in varied shapes and sizes.

Mammilary or Cloud: Carbonate coatings that form underwater in cave pools, around projections and rocks lining the pool, whose water is super-saturated with calcium carbonate.

Raft: Delicate, doily-like sheet of calcite or aragonite that sometimes occurs on the surface of a still, supersaturated cave pool.

Raft cone: A heap of sunken cave rafts.

Rimstone: Very thin calcite rims. on the edges of pond streams or shallow pools in caves.

Shield: Calcite disk created when calcite-rich seep water under hydrostatic pressure is forced from tiny cracks in a cave wall, ceiling or floor.

Shelfstone: A ledge or projection (usually calcite) extending from the edge of a cave pool or attached to a speleothem dipped in a cave pool.

Soda Straw: Hollow, elongate, generally translucent tube of calcite representing the earliest growth of stalactites. They are equal in diameter to the water drops conducted along their length.

Stalagmite: A post of dripstone growing up from a cave floor.

Stalactite: An icicle-shaped accumulation of dripstone hanging from a cave roof.

-- A.R. Royo


Calcite, the Mineral
Desert Environment & Geology Index
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Carlsbad Caverns National Park

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