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Moonmilk (sometimes called mondmilch, also known as montmilch or as cave milk) is a white, creamy substance found inside limestone, dolomite, and possibly other types of
cave A cave or cavern is a natural void in the ground, specifically a space large enough for a human to enter. Caves often form by the weathering of rock and often extend deep underground. The word ''cave'' can refer to smaller openings such as se ...
s. It is a
precipitate In an aqueous solution, precipitation is the process of transforming a dissolved substance into an insoluble solid from a super-saturated solution. The solid formed is called the precipitate. In case of an inorganic chemical reaction leading ...
from
limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms wh ...
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, macr ...
s of varying composition usually made of
carbonate A carbonate is a salt of carbonic acid (H2CO3), 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 g ...
s such as
calcite Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on the Mohs scale of mineral hardness, based on scrat ...
,
aragonite Aragonite is a carbonate mineral, one of the three most common naturally occurring crystal forms of calcium carbonate, (the other forms being the minerals calcite and vaterite). It is formed by biological and physical processes, including prec ...
,
hydromagnesite Hydromagnesite is a hydrated magnesium carbonate mineral with the formula Mg5(CO3)4(OH)2·4H2O. It generally occurs associated with the weathering products of magnesium containing minerals such as serpentine or brucite. It occurs as incrustations ...
, 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. Monohydrocalcit ...
. There are several hypotheses concerning the origin of moonmilk. One of these explains moonmilk to be the result of
bacterial Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...
action rather than from chemical reactions. According to this particular hypothesis, moonmilk is thought to have been created by the bacterium '' Macromonas bipunctata''. However, no microbiological studies have been carried out so far. Moonmilk was originally explained as created by
moon The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width ...
rays. It is possible that moonmilk is formed by water that dissolves and softens the
karst Karst is a topography formed from the dissolution of soluble rocks such as limestone, dolomite, and gypsum. It is characterized by underground drainage systems with sinkholes and caves. It has also been documented for more weathering-resistant ...
of caves consisting of carbonates, and carries dissolved nutrients that can be used by microbes, such as
Actinomycetes The Actinomycetales is an order of Actinomycetota. A member of the order is often called an actinomycete. Actinomycetales are generally gram-positive and anaerobic and have mycelia in a filamentous and branching growth pattern. Some actinomycete ...
. As the microbial colonies grow, they trap and accumulate chemically precipitated crystals in the organic matter-rich matrix formed that way. It has been suggested that 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 Respiration may refer to: Biology * Cellular respiration, the process in which nutrients are converted into useful energy in a cell ** Anaerobic respiration, cellular respiration without oxygen ** Maintenance respiration, the amount of cellul ...
and possibly
organic acids An organic acid is an organic compound with acidic properties. The most common organic acids are the carboxylic acids, whose acidity is associated with their carboxyl group –COOH. Sulfonic acids, containing the group –SO2OH, are rel ...
, may help to dissolve the carbonate. In 2017, archæologists at the
University of Chinese Academy of Sciences The University of the Chinese Academy of Sciences (UCAS; ) is a public university for graduate education, under the direct leadership of the Chinese Academy of Sciences (CAS). The predecessors of UCAS are the Graduate University of the Chinese ...
in China discovered a bronze jar dating to over 2,700 years ago containing animal fat combined with moonmilk, believed to have been a cosmetic face cream used by Chinese noblemen. Being soft, moonmilk was frequently the 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 world's largest formation of
brushite Brushite is a phosphate mineral with the chemical formula . Crystals of the pure compound belong to the monoclinic space group C2/c and are colorless.Kartchner Caverns State Park in southern Arizona. In the middle of 16th century moonmilk was used as a medicine according to Gessner, and continued to be used as such until the 19th century. It is said to have cured
acidosis Acidosis is a process causing increased acidity in the blood and other body tissues (i.e., an increase in hydrogen ion concentration). If not further qualified, it usually refers to acidity of the blood plasma. The term ''acidemia'' describes t ...
and probably cardialgia by neutralizing an overdose of acid. It had no adverse health effects.''Moonmilk''
in showcaves.com.


References

* George W. Moore and Nicholas Sullivan. ''
Speleology Speleology is the scientific study of caves and other karst features, as well as their make-up, structure, physical properties, history, life forms, and the processes by which they form ( speleogenesis) and change over time (speleomorphology ...
: Caves and the Cave Environment'', rev. 3rd ed. Dayton, Ohio: Cave Books, 1997. (hardcover), (paperback).


External links


Moonmilk and Cave-dwelling Microbes





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