In the ancient world, Pyxides were most often used by women as cylindrical boxes for cosmetics, jewellery, or trinkets. This particular piece no longer has its lid. These vessels often accompanied their owner all the way to the grave, with many recovered from burials. Sometimes pyxides functioned as votive offerings in the sanctuaries of female deities.
The iridescence on ancient Roman glass is caused by weathering on its surface. The extent to which a glass object weathers depends mainly on the burial conditions; however, the humidity, heat, and type of soil in which the glass was buried also all affect its preservation.
To find out more about Roman glass please see our relevant blog post: Ancient Glass and Collecting Roman Glass.