Context: I'm reading the first volume of "The Twelve Kingdoms" (月の影・影の海). The protagonist, Yoko, is in the school's staff room when a strange man appears and tells here she is in danger. Indeed, a window pane next to her suddenly breaks - the sentence that says this is "裏庭側の窓ガラスが割れたのは".
The last sentence in the chapter is:
My question: Why is ガラスというガラス used here rather than simply ガラス?
When I looked for "ガラスというガラス" in Google, it seems to be used to describe types of glass "glass called 'crystal glass'" and the like. Which makes sense. But this doesn't seem to fit with this sentence.