Opalite
Opalite is a trade name for synthetic opalised glass and various opal simulants. It is also used to promote impure varieties of variously colored common opal. Opalite is sometimes called the Tiffany Stone or Bertrandite. Inside of opalite there appears to be a rainbow. You can read through Opalite, because it is translucent. The streak of opalite (depending on the color) is typically white.