I think there is definitely a need for a visual glossary. As you have already discovered, there are a lot of "nebulous" terms used by numismatists that do not really have a solid foundation. When we say that a coin is "porous" or "crystalline" most people who have seen a lot of coins will understand what that means. But, what is the difference between porous and pitted? or corroded? As Bruce points out, what passes as "crystalline" may simply be the leaching of certain elements from the composition. I have taken to describing surface conditons simply as "smooth" or "rough". This is a very loose terminology, but most people at least understand the terms.
Wayne G. Sayles