We wanted to get some rocks to use as ornaments in our vegetable garden, and the simplest thing seemed to buy a few bags of these "Caribbean Beach Pebbles" from Home Depot. When they were delivered we noticed that the rocks all seem to be coated in a fine white powder, roughly the texture of talcum or chalk dust.
Does anybody know what this powdery stuff is? Is it just the rock itself, or are they coated with something? And is there any reason to be concerned that whatever it is might get into the soil and harm the vegetables in the garden?