The oyster makes treasure from irritation — the grit coated in nacre until it is pearl. It names the transformation of the bothersome into the precious, and the world-as-oyster's promise: the closed thing openable to riches.
Positive Resonance
Irritation transformed to pearl, the closed world openable
Shadow Aspect
Sealed shut against inspection, the pearl requiring the knife
Nuances
The pearl inside: irritation transmuted
Shucking: the closed opened by force
The world your oyster: everything openable in principle