We all know earthworms and might consider them slimy and scary, beneficial to our garden, or chicken feed. What is not very well known is that many earthworm species produce calcite (the stuff that e.g. oysters are made of) as tiny granules produces in specialised glands. Darwin already described this in his last book, and hypothesised they might have something to do with excretion or digestion, but the reason why these granules are produced is still a mystery.
Earthworm granules are quite often found in archaeological finds and buried soils. I investigate if their chemical composition can be used to reconstruct past climate and environments, in a similar way as this is done using corals or shells.