While i was looking at your site I saw that you mentioned a Vineger test, so I looked it up and found this: "One trick to test rocks is to put a
few drops of vineger (sp?) on it. If after a few minutes it starts to
foam, then don't use it in the tank as this is an indication that the
rock will slowly dissolve in your tank. Also avoid any rocks that
appear to have any veins of metal running through them." is that what you where referring to?