Geosmin (FEMA# 4682, CAS# 23333-91-7) has a distinct earthy or musty odor.
Geosmin is responsible for the earthy taste of root vegetables and a contributor to the strong scent - “Petrichor” that occurs in the air when rain falls after a dry spell of weather or when soil is disturbed. In chemical terms, it is a bicyclic alcohol with formula C12H22O, a derivative of Decalin. Its name is derived from Ancient Greek.
The odor detection threshold of Geosmin is very low, ranging from 0.006 to 0.01 micrograms per liter in water. Substantivity: 68 hours @ 100 %.