A prism that was gifted to Cassandra Fraiser.
A Prism is a transparent object that bends light. It breaks white light up into its component colors, which make up the rainbow, to form a spectrum.
History[]
In 2001, on Cassandra Fraiser's sixteenth birthday, Dominic gifted her a pyramid-shaped prism to decorate her room with, since she had said the ones from class were pretty. Cassie held it up to the light, shining a rainbow onto Dominic's face, before the two kissed and she collapsed. (SG1: "Rite of Passage")