Salty Residue on Rocks?

[MikeinBrooklyn]

I have a question. I have noticed a salty residue left on the tops of the rocks in my pond when evaporation has gotten ahead of me. I say "salty" because it looks like the salt that is left on an unwashed car during snowy winters. My pond is clear and I am not having any issues and I use a bog filter. Is it just a sign of hard water or is it something more sinister I should be concerned about?

 

[Jhn]

Usually just a sign of hard water, left over calcium from evap. called limescale.

 

[Johnan3]

I notice this same residue on my pond lights that are in my waterfall and pond. I presumed this was the hard water and it was calcium residue. It has not hurt my pond values as I get those tested. Will watch your thread to see if others can provide good feedback.

 

[Chucker's 50]

Can't be sure, but more than likely lime deposits.