Scheme to cut precious stone in multiple layers (6)
I believe the answer is:
strata
'layers' is the definition.
(stratum is a kind of layer)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for strata that I've seen before include "hard beds" , "Layers of sedimentary rock" , "Layers or social classes" , "Levels, grades or social classes" , "Parallel layers" .)