Clear, Reflective Material
This page is the CodyCross answer for the clue below from Paris, Group 259, Puzzle 3 (The Army Museum).
Question is: Clear, Reflective Material
and the answer is: CRYSTAL
Word Meaning:
CRYSTAL — (countable) A solid composed of an array of atoms or molecules possessing long-range order and arranged in a pattern which is periodic in three dimensions.
Definitions from Wiktionary.