Mango stone

Is it safe for bunnies to chew this?
Mum gave the bunnies the central stone with a little bit of mango flesh still on it at the weekend. They've completely stripped all the flesh off it and have nibbled through the outer shell bit of the stone and eaten some of the inner seed.
Two days later and they're still alive and kicking, but should I tell Mum not to do it again? I know all fruits should only be given rarely but as a very occassional treat is it okay? I've found sites that say mango flesh is okay, but no one's mentioned the stone. :?

A lot of fruit stones are extremely poisonous, so I wouldn't risk it - they often contain arsenic although I don't know about mango stones - I'd give them something else to play with :?

I'm sure I read somewher that mango stones are bad for animals.

Yep - that was my gut feeling too. It's probably hallucinogenic the way Flop was guarding it - I distracted him with a pine cone though! Thanks for the opinions