Reveal progress of HDD encryption process?

I am in the middle of an encryption process right now for one of my external HDDs and it's taking a long time, but I only know it's working based on two criteria: firstly, that the HDD is working (the external light is blinking), and secondly that the HDD is not mounted (during the encryption process) but obviously active.

However, there is no clear indication of progress on the encryption process, it not mounted I can understand why, but I would expect there to be something?

Is there a hidden Terminal command that can reveal the progress of an the encryption process in real-time?