When we bought our home in 1958, a small place, to be sure, it obviously didn't have all the modern conveniences or the best quality products. Eventually, the toilet began to have a dark look - black, actually, that could never be cleaned. After some time it got pretty disgusting and my husband replaced the toilet. Things went well for a number of years, until I decided I wanted to modernize our bathroom. I had no intention of changing the toilet or the lavatory but the tub had developed the same blackish appearance. Along with the baby blue and pink tiles, this tub had to go! Well, in busting out the tiles, a chip apparently ricocheted and hit our toilet. The tile contractor begrudgingly replaced the toilet (4 - 5 years ago) and - you guessed it, the toilet is beginning to develop this black look again. What is this stuff? Does it have anything to do with the quality of the fixture? I'm not happy with the thought of buying another toilet but if I do, I'd like to know if I can get one that will perform better and longer than these things I've had before. Thanks for any help.