Speleothems

thumb|300px|right|Image showing the six most common speleothems with labels. Enlarge to view labels.

thumb|upright=1.75|Image showing the six most common speleothems thumb|upright|The "Witch's Finger" in Carlsbad Caverns, New Mexico

thumb|upright=1.4|Cave labeled with the six most common types of speleothems: flowstone, columns, drapery, [[stalagmites, stalactites and straws]] A speleothem (; ) is a geological formation made by mineral deposits that accumulate over time in natural caves. They can take a variety of forms, depending on their depositional history and environment. Common forms include stalagmites, stalactites, and flowstones.

thumb|Rare "fishtail" helictites in the Caverns of Sonora near [[Sonora, Texas]] thumb|A helictite at Treak Cliff Cavern in [[Derbyshire]]

right|thumb|Diagram of dripstone cave structures (moonmilk is labelled I)

mineral formation found in caves

thumb|Boxwork in Wind Cave, South Dakota In geology, boxwork is defined as a honeycomb-like structure that can form in some fractured or jointed sedimentary rocks. If the fractures in the host rock are mineralized, they can become more resistant to weathering than the surrounding rock, and subsequent erosion can produce boxwork structures. In mining geology, boxwork is a set of (typically) quartz-lined cavities, retaining the shape of the dissolved ore minerals, in gossans. In classical geology or mineralogy these mineral casts would not be called boxwork, but would instead be called pseudomor

thumb|300px|Rimstone – Endless Caverns, Virginia thumb|Rimstone with odd color, From Bristol Caverns 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

thumb|''Saracen's tent'' in Luray Caverns in [[Virginia is considered to be one of the most well-formed flowstone draperies in the world]]

thumb|450px|right|Snottites in Cueva de Villa Luz in Southern Mexico

tubular form of cave mineral deposit

common cave formation

solenoid percussion instrument

snowflake-like speleothem

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thumb|upright|Calthemite straw stalactite growing from the concrete ceiling of an undercover car-park thumb|upright|Calthemite straw stalactites, the rightmost example demonstrating bending due to the direction of air currents during its formation