Murano glass is hand-crafted by masters working the heated-up liquefied glass mass using special centuries-old techniques, and then cooling it down till it solidifies to form a specific pattern within a certain shape. For this reason, when an article made of Murano glass breaks, it is not possible to fix it except for gluing it together. Gluing may work if the item has a smooth break line and broke into only two or three pieces as opposed to many small ones.
If, based on the above conditions, you feel that it may be possible to glue the item back together, first of all you need to buy the right glue. We recommend using E-6000® glue for Murano glass, or any glass for that matter. This is a very strong waterproof and flexible adhesive once it dries. The only downside is its long drying time- make sure to let it dry for 24 to 72 hours after application. With this glue, apply a thin coat to both glass surfaces that you need to attach, wait ten minutes and strongly press the surfaces together. Then put the item aside and let dry. Make sure you use this glue only in an area that has adequate ventilation.
If your Murano glass broke in such a way that it can’t be glued together, or if it just cracked inside its frame (like may be the case with Millefiori pendants), your best option may be to try to find a replacement. Regardless of whether the Murano glass item was modern or vintage, purchased recently or long ago, there are companies specializing in Murano glass that will be willing to work with you to find a replacement. GlassOfVenice.com is one such company, which accepts custom requests and is often able to deliver the specified products.