So, I am putzing around with my eevee who is holding an everstone. I am going to use a fire stone on my vulpix but I accidentally click on eevee. Would eevee evolve?
DISCLAIMER I would never be so careless.
Yes it will
Another stone, the Everstone, is different in that radiates a type of energy that prevents evolution in the holders; however, if a Pokémon holding the Everstone has an evolutionary stone used on it, it will still evolve.
Source