I read that salt may be responsible for the black spots on my mint plant so i started taking out the white stones from the earth in my pots i noticed an improvement in the plant and was relieved however when i went to the nursery and questiones the sales person they said the white rocks were perlite. which is it? Perlite or salt?
Particles that big sounds like perlite, especially if they are porous and easily can be crushed with your fingers.
This page has a picture of vermiculite. Gardening With Vermiculite – Vermiculite Uses And Information. I don't remember it having white stone-looking things, though I suppose they could have been added to the mix.
