Laminated mineral
I believe the answer is:
mica
'laminated mineral' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for mica that I've seen before include "Muscovite with perfect cleavage" , "Flexible mineral found in igneous and metamorphic rocks" , "Shiny silicate mineral" , "Isinglass" , "Transparent mineral" .)