What does the destruction of the conch symbolize in Lord of the Flies?

The destruction of the conch symbolizes the final collapse of law, democratic order, and civilized speech among the boys. From the beginning, the conch has gathered the boys into assemblies and given its holder the right to speak, so it stands for their attempt to create a society based on fair rules rather than force.

Its destruction happens at Castle Rock, where Ralph, Piggy, Sam, and Eric go to demand the return of Piggy’s glasses. Piggy clings to the conch because he still believes that moral argument and agreed-upon rules can matter. His plan is to appeal to Jack because “what's right's right,” and when he raises the conch, he makes one last argument for sense and order over savagery. The setting itself makes that appeal feel doomed: Jack’s tribe is armed, Samneric are seized, and Jack demonstrates his power by saying, “See? They do what I want.”

Roger’s boulder kills Piggy and smashes the conch at the same moment, linking the destruction of reason with the destruction of law. Piggy symbolizes intelligence and rational thought, and the conch symbolizes lawful order. When both are crushed together, the boys’ society loses the two forces most opposed to Jack’s rule: reasoned speech and shared rules. Afterward, Jack throws his spear at Ralph with deadly intent, and Ralph flees into the jungle. The old system gives way to domination and fear.

The conch’s destruction also shows how fragile the boys' makeshift civilization has been all along. The boys treated the conch as powerful only while they chose to believe in it. Once Jack’s tribe rejects its authority, the shell's delicacy becomes obvious, just as their social order proves breakable under violence and the desire for power.