Off topic...I was once in a queue behind a lady who was allowed to take a rock in her hand luggage, 'as a souvenir'. Im talking 40cm square bit of slate. If that cant be used as a weapon, Im not sure what can.
Yes, but to what end? Things are only more dangerous in the air than on the ground if they can cause a crash or let you take over the plane. A rock is no more dangerous on a plane than it would be in a shopping mall. Yes, you might hit and even kill someone, but then you would be overpowered by the passengers, restrained and arrested when you touch the ground.
For that matter, they only stop bladed weapons as "security theatre". You couldn't take control of a plane with a stanley knife anymore. On 11/9 they threatened a flight attendants life if they weren't let into the cockpit. Now the passengers and crew would understand that letting them into the cockpit means they will all die, so that is no longer a way to get control of plane.
(yes, and if some looney ever tries to hijack a plane with a big rock, they will ban them. note looney will not succeed in hijack)