10 February 2013

Squeezing iron out of a stone

Iron is the second most abundant metal on Earth (next to aluminium).  About 3000 years ago human beings figured out how to extract it from rock, a skill that catapulted mankind into an era of self-determination and dominion over nature. Yet some crustose lichens, which grow on and in stone, have been doing this quietly for millions of years. Take a walk along forestry tracks into the hills in any of the valleys in Neath Port Talbot and look out for rusty-red stained rocks colonised by these amazing organisms. Two species, in particular, should draw your attention.

Lecidia lithophila (above) is a fairly common upland lichen able to extract iron from rock, which results in an attractive stone mosaic with characteristic rusty staining that is difficult to miss. The black pimples are apothecia, spore producing structures formed by the fungal part of the lichen.

Porpidia macrocarpa (above) can also do this, often with much greater effect so that the whole of the surface of the stone can become rusty-red in colour. Note the very large black apothecia (up to 3mm in diameter) which are a characteristic of this species.
While an ability to make a living growing on rock has to be admired, extracting iron out of stone is something else!

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