If I might be so presumptious as to illustrate what DWF is saying with an analogy that many here on teh StyleForvm will understand: It is like the difference between Americans and Canadians on one hand, and Europeans on the other. Americans and Canadians (and by "Canadian" I, of course, exclude French Canadians) tend to shower and bathe every day. This habit helps to remove microfine particles of ground rock, old coke bottles, etc. Europeans, in contrast, do not. They tend to rub lotion on their bodies and to douse themselves with cologne instead of bathing. This just moves the dirt around...including obsidian glass that settles on the body from the periodic eruptions of Vesuvius (a cone-shaped mountain near Naples.) I hope that was helpful. - B Helpful and apt. Here in the "upper left-hand corner" Vesuvius is but a shadow to Mt. Mazama. If obsidian weren't black (or sometimes red) we could see the earthworms for catching bullheads.