What a great question.
I assume one would be able to see vortexes and have occasionally noticed unusual energy formations when I've been out in nature, but have never double checked with my dowsing rods. I'll have to check next time I see one of those and have my dowsing rods handy.
Have you checked to see if you can visually perceive any vortexes you are aware of?
I'll have to do another posting once I get a chance to experiment with this.
All the best!