Cave popcorn
![](http://upload.wikimedia.org/wikipedia/commons/thumb/6/6d/Cave_popcorn_trays.jpg/220px-Cave_popcorn_trays.jpg)
Cave popcorn, or coralloids, are small nodes of calcite, aragonite or gypsum that form on surfaces in caves, especially limestone caves.[1][2] They are a common type of speleothem.[1][2]
Appearance
The individual nodules of cave popcorn range in size from 5-20 mm and may be decorated by other speleothems especially aragonite needles or frostwork.[1][2] The nodules tend to grow in clusters on bedrock or the sides of other speleothems.[1] These clusters may terminate suddenly in either an upward or downward direction forming a stratographic layer.[1] When they terminate in a downward direction, they may appear as flat bottomed formations otherwise known as trays.[1]
The color of cave popcorn is usually white but various other colors are possible depending on the composition.[2]
Formation
Cave popcorn can form by precipitation by the loss of CO2.[1] When formed in this way the nodules have the characteristics of small balls of flowstone.[1] It can also form by evaporation in which case it is chalky and white like edible popcorn.[1] In the right conditions, evaporative cave popcorn may grow on the windward side of the surface to which it is attached or appear on the edges of projecting surfaces.[1]
References
"Cave Popcorn or Coral." Underground Adventures. Sierra Nevada Recreation Corp,
2006. Web. 2 May 2012. <http://www.caverntours.com/ KIDSPAGE_Form_Popcorn.html>.