There are bacteria in a certain cave system that draws energy from the mineral deposits. They get 0 energy from the sun.

A little searching found: http://newsinfo.iu.edu/news/page/normal/4229.html

I don't think that this is the bacteria that I was thinking of. The one the I'm thinking of was mentioned in the Planet Earth episode on caves.

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http://dsc.discovery.com/news/2009/05/08/cave-bacteria-mars....

http://en.wikipedia.org/wiki/Lechuguilla_Cave

  "Rare, chemolithoautotrophic bacteria are believed to
  occur in the cave. These bacteria feed on the sulfur,
  iron, and manganese minerals and may assist in enlarging
  the cave and determining the shapes of some unusual
  speleothems. Other studies indicate that some microbes
  may have medicinal qualities that are beneficial to
  humans.[1]"

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