geosmin

noun1

1. •
   A bacterial derivative of decahydronaphthalene that has a strong earthy smell and is the material responsible for petrichor and for the earthy taste of beetroot.

   • A good example of this is geosmin, for which a typical sensitivity for the human nose is below 10 parts per trillion (10 parts in 10¹⁸ v/v) (ppt). — 1998