Do circle glass prisms exist? Can they refract light? What is a circle prism? Please explain.?

A circle glass prism. Do those exist? If so, do they diffract, or refract light? Does light division into the rainbow colors happen inside the circle prism too? A circle prism is a sphere actually. So, please explain how a circle prism works, and how it can divide lught into the 7 colors. Thank you!