What does the stone from "The Stone" symbolize

I believe it symbolizes things that don’t grow or change.

Explanation:

cassius, casca, and their allies plant false documents to manipulate brutus to join their cause to remove caesar. after doing so, they visit brutus at night in his home to persuade him of their views. there they plan caesar's death. brutus is troubled but refuses to confide in his devoted wife, portia. on 15 march, caesar's wife, calpurnia, urges him not to go to the senate. she has had visionary dreams and fears the portents of the overnight storms.