....like a Ridgid #276 or Reed SC49-6. What are the cutting wheels made
of? How easy are they to ruin?

My brother is a school teacher and wants to get a bunch of geodes
(hollow rocks) for the kids to break open. From what I've read, they
are commonly cracked using a soil-pipe cutter, which start at $350. If
he rents one, is he probably gonna ruin the cutters and have to buy a
new chain for it when he turns it in?

Thanks, regards,
Bob