Some colors of glass are widely known. Perhaps the best example of this is “cobalt blue” that is produced by adding cobalt oxide to the glass melt. “Vaseline glass” is a fluorescent yellow-green glass that contains small amounts of uranium oxide. “Ruby gold” and “cranberry glass” are red glasses produced by the addition of gold. “Selenium ruby” is a red color caused by the addition of selenium oxide, and “Egyptian blue” is produced by the addition of copper.