Each bead is completely unique as the application method and dichroic achieve a different result in each bead. The size is approximately 14mm round with a base of transparent Moretti Glass. They are exquisite and dichroic glass is a great way to upscale your Venetian Jewelry.
A dichroic filter or thin-film filter is a very accurate color filter used to selectively pass light of a small range of colors while reflecting other colors (from Wikipedia).