Moonmilk (sometimes called mondmilch, also known as bergmilch, montmilch, or cave milk) is a white, creamy substance found inside limestone, dolomite, and possibly other types 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. It is a

precipitate In an aqueous solution, precipitation is the "sedimentation of a solid material (a precipitate) from a liquid solution". The solid formed is called the precipitate. In case of an inorganic chemical reaction leading to precipitation, the chemic ...

from

limestone Limestone is a type of carbonate rock, carbonate sedimentary rock which is the main source of the material Lime (material), lime. It is composed mostly of the minerals calcite and aragonite, which are different Polymorphism (materials science) ...

comprising aggregates of fine

crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macros ...

s of varying composition, usually made of

carbonate A carbonate is a salt of carbonic acid, (), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word "carbonate" may also refer to a carbonate ester, an organic compound containing the carbonate group ...

s such as

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 ...

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 ...

hydromagnesite Hydromagnesite is a hydrated magnesium carbonate mineral with the formula . It generally occurs associated with the weathering products of magnesium containing minerals such as serpentine group, serpentine or brucite. It occurs as incrustations a ...

, and/or

monohydrocalcite Monohydrocalcite is a mineral that is a hydrous form of calcium carbonate, CaCO3·H2O. It was formerly also known by the name hydrocalcite, which is now discredited by the IMA. It is a trigonal mineral which is white when pure. Monohydrocalcite ...

Formation and Composition

Moonmilk forms as a result of several processes, including both chemical reactions and possible bacterial action. One hypothesis suggests that moonmilk is created by the bacterium '' Macromonas bipunctata''. However, no microbiological studies have been carried out to confirm this. Moonmilk was originally thought to be created by

moon The Moon is Earth's only natural satellite. It Orbit of the Moon, orbits around Earth at Lunar distance, an average distance of (; about 30 times Earth diameter, Earth's diameter). The Moon rotation, rotates, with a rotation period (lunar ...

rays, a misconception reflected in its name. It is possible that moonmilk forms when water dissolves and softens the

karst Karst () is a topography formed from the dissolution of soluble carbonate rocks such as limestone and Dolomite (rock), dolomite. It is characterized by features like poljes above and drainage systems with sinkholes and caves underground. Ther ...

in caves, carrying dissolved nutrients that are used by microbes, such as

Actinomycetes The Actinomycetales is an Scientific classification, order of Actinomycetota. A member of the order is often called an actinomycete. Actinomycetales are generally Gram-positive bacteria, gram-positive and anaerobic and have mycelia in a filamento ...

. As microbial colonies grow, they trap and accumulate chemically precipitated crystals in an organic matter-rich matrix. These

heterotrophic A heterotroph (; ) is an organism that cannot produce its own food, instead taking nutrition from other sources of organic carbon, mainly plant or animal matter. In the food chain, heterotrophs are primary, secondary and tertiary consumers, but ...

microbes, which produce CO₂ as a waste product of respiration and possibly organic acids, may help to dissolve the carbonate.

Historical and Cultural Uses

In 2017, archaeologists at the University of Chinese Academy of Sciences in China discovered a bronze jar dating back over 2,700 years, containing animal fat combined with moonmilk. This mixture is believed to have been used as a cosmetic face cream by Chinese noblemen. Being soft, moonmilk was frequently used as a medium for finger fluting, a form of

prehistoric art In the history of art, prehistoric art is all art produced in preliterate, Prehistory, prehistorical cultures beginning somewhere in very late geological history, and generally continuing until that culture either develops writing or other met ...

. The Swiss naturalist

Conrad Gessner Conrad Gessner (; ; 26 March 1516 – 13 December 1565) was a Swiss physician, naturalist, bibliographer, and philologist. Born into a poor family in Zürich, Switzerland, his father and teachers quickly realised his talents and supported him t ...

described moonmilk's use as a medicine in the 16th century. It continued to be prescribed until the 19th century.''Moonmilk''
in showcaves.com.

Notable Formations

The world's largest formation of brushite moonmilk is found in the Big Room of Kartchner Caverns State Park in southern Arizona.

References

External links

Moonmilk and Cave-dwelling Microbes

Novedades Rio Subterráneo de Leche de Luna
(Spanish) Speleothems {{bacteria-stub