Use 'crystalline' to describe something transparent and free from any cloudiness or distortions. Through the crystalline glass, one could see each pebble at the bottom of the stream.
Pro Tip 2/3
Pure Quality
'Crystalline' often implies purity or perfection of the object being described. The jeweler praised the crystalline quality of the diamond.
Pro Tip 3/3
Metaphoric Use
'Crystalline' can be used metaphorically to describe clarity in abstract concepts. Her explanation was crystalline, leaving no room for confusion.