Moonmilk

{{Infobox rock

| name = Moonmilk

| alternative_name = Mondmilch, Montmilch, Cave milk

| type = Speleothem

| type_link = Speleothem

| image = Bergmilchkammer 04.jpg

| image_size = 250px

| alt =

| caption = Moonmilk ostensibly created from Macromonas bipunctata in the cave Bergmilchkammer

| coordinates =

| composition = Carbonates (e.g., calcite, aragonite, hydromagnesite, monohydrocalcite)

| texture = Creamy, soft

}}

File:Tropfsteine.svg

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 caves. It is a precipitate from limestone comprising aggregates of fine crystals of varying composition, usually made of carbonates such as calcite, aragonite, hydromagnesite, and/or 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 rays, a misconception reflected in its name.{{cite book |last=Gessner |first=Conrad |authorlink=Conrad Gessner |title=Descriptio Montis Fracti sive Montis Pilati |trans-title=Description of Mount Fractus, or Mount Pilatus |date=1555 |language=Latin |page=54 |url=http://gallica.bnf.fr/ark:/12148/bpt6k93851n/f59 |access-date=March 12, 2016}}

It is possible that moonmilk forms when water dissolves and softens the karst in caves, carrying dissolved nutrients that are used by microbes, such as Actinomycetes. As microbial colonies grow, they trap and accumulate chemically precipitated crystals in an organic matter-rich matrix. These heterotrophic microbes, which produce CO₂ as a waste product of respiration and possibly organic acids, may help to dissolve the carbonate.{{cn|date=March 2020}}

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.{{cite web | last=Marshall | first=Michael | title=2700-year-old face cream was made from animal fat and cave 'milk' | website=New Scientist | date=2019-02-26 | url=https://www.newscientist.com/article/2266855-2700-year-old-face-cream-was-made-from-animal-fat-and-cave-milk/ | access-date=2021-02-08}}

Being soft, moonmilk was frequently used as a medium for finger fluting, a form of prehistoric art.

The Swiss naturalist Conrad Gessner described moonmilk's use as a medicine in the 16th century. It continued to be prescribed until the 19th century.[http://www.showcaves.com/english/explain/Speleothem/Moonmilk.html Moonmilk] {{Webarchive|url=https://web.archive.org/web/20120531093129/http://www.showcaves.com/english/explain/Speleothem/Moonmilk.html |date=2012-05-31 }} 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.{{cite news|last1=Cronkite|first1=Amy|title=State celebrates 10 years of Kartchner Caverns Big Room tours|url=http://tucson.com/news/local/state-celebrates-years-of-kartchner-caverns-big-room-tours/article_10c9688f-9273-5aa6-8420-966983789252.html|accessdate=27 February 2015}}

References

External links

[http://www.craterlakeinstitute.com/online-library/nature-notes/vol26-cave-dwelling-microbes.htm Moonmilk and Cave-dwelling Microbes]
[https://web.archive.org/web/20090722094310/http://web.mst.edu/~microbio/BIO221_2001/micromonas_bipunctata.html Micromonas bipunctata]
[http://www.goodearthgraphics.com/virtcave/moonmilk/moonmilk.html The Virtual Cave: Moonmilk]
[http://www.aranzadi-zientziak.org/fileadmin/docs/espeleologia/AlzolaBiolTr.pdf Novedades Rio Subterráneo de Leche de Luna] (Spanish)

Category:Speleothems