This is what the entry from the Zecchi site looks like to help in ordering: “ (DIOPTASIO) - -Natural green crystal (Copper silicate) powder - Icon pigment- .” Here is our best guess at the equivalent in Italian. This is from the Italian portion of the site: “ (DIOPTASIO) - Cristallo verde (silicato di rame) -in polvere- PER ICONOGRAFIA -.”