See Lattimo .

To understand what is the opalino glass, it's necessary to know what the lattimo is.
The lattimo glass is a white opaque glass, invented in Murano during the second half of the 15th Century to imitate the first porcelains that were so trendy at that time in Europe.
The special finish creates an effect similar to an opal, a stone of milky white and blue colour, rich of iridescences . Hence the name lattimo (from latte , milk) or opalino ( from opal).