Blows my mind: Something I never imagined or something unexpected.
Ex:
John says, "This is going to blow your mind, but glass is actually a liquid."
Jane responds, "Wow, really?"
Since glass is very solid looking, it is beyond imagination or unexpected when someone learns it is a liquid.
Jura, your examples are not 'exciting' enough. I wouldn't see that kind of response. It is usually the person who is telling the information who says "this will blow your mind".