Well I was very excited to see the local Lowe's get the smaller sized lava rock. So, I picked some up to even out the organic/inorganic balance of my soil. But, after working with it a bit, I noticed that my hands were bright red! Is that a natural property of red lava rock or is it colored for appearance? I know people use this stuff for top dressing or decorating in their gardens, flower beds, etc. But can it be harmful in the smaller confines of a bonsai pot?