Okay, so the Mexican Talavera tile--while earthy and beautiful--is not going to work for this particular mosaic project. Unfortunately, the stuff flakes, cracks, chips, and generally doesn't cut in the shape I want. I am going to keep it for a future project where shape isn't quite as important.
Sigh...I'm off to find new tiles. Good news is I found a tile store that allows you to buy in quantities as small as a square foot and they send free samples.