Dear Linda 1470- the correct term is Aventurine. In the glass world the term is used for a manmade glass that has metallic flakes.By the beginning of the 19th century, chromium was used to bring about green. Potassium chromate produced yellow in certain types of glass. Chrome oxide, that crystallized out of heavily leaded glass, provided the metallic glitter in green aventurine. Most , if not all were made by Peltier glass and are beautiful marbles I hope you don't think I am butting in, just trying to help.F/W/B-