Exoglass was a type of glass.
By the year, 200,100, exoglass was used in the construction of the Big Brother House aboard the Game Station. As Lynda Moss claimed to the Ninth Doctor that he would need a nuclear bomb to get through it. Indeed, he found that sonic screwdriver had no effect. (TV: Bad Wolf)
By 5,000,000,000, exoglass made up the windows of the space station Platform One. Though it could be penetrated by the rays of the Sun, it was capable of self-repair, but only whilst sun filters relieved stress from the glass. (TV: The End of the World)