Due to the presence of vanabins, concentration of vanadium found in the blood cells of Ascidia gemmata belonging to the suborder Phlebobranchia is 10,000,000 times higher than that in the surrounding seawater. A similar biological process might have played a role in the formation of vanadium ores.
Vanadium is also present in fossil fuel deposits such as crude oil, coal, oil shale, and oil sands. In crude oil, concentrations up to 1200 ppm have been reported.