Opalescent glass is a type of glass that exhibits a milky, translucent quality, often resembling the iridescence of an opal gemstone. This effect is achieved by adding specific minerals during the glass-making process, which scatter light and create a soft, glowing appearance. It is commonly used in decorative items, lampshades, and stained glass windows. The unique visual properties of opalescent glass can change depending on the angle of light and the viewer's perspective. Popular in the late 19th and early 20th centuries, it was notably produced by companies like Fenton Art Glass and Louis Comfort Tiffany, who crafted beautiful pieces that are now highly collectible.