Hi Bat20,
I think the glitter effect in your weight is aventurine. It is included in many glass objects because of its shimmer... Gold aventurine is more often used, but aventurine exists in all the colours of the rainbow. Here you have green aventurine.
Although it is commonly used by glass artists, aventurine is very frequently used by Murano glass-makers and its inclusion is seen a Murano glass-making trait (see the image of a 3Fiori weight below). Having said that your weight does not strike me as Murano (but as I have said it is resorted to by many glass artists).
SophieB