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".

blow (one's) mind Slang To affect with intense emotion, such as amazement, excitement, or shock. http://www.thefreedictionary.com/blow+mind

It blows my mind= It really amazes and shocks me. Examples: 1.Bill: Did you hear about Tom's winning the lottery? Sue: Yes, it blows my mind! 2. John: Look at all that paper! What a waste of trees! Jane: I agree. It blows my mind!