On Fri, 20 Mar 2015 17:48:22 GMT, azigni wrote:

I am guessing here, but because the cactus did not come where you live,
but was shipped there, the glued pebbles are to ensure the pot and cactus
did not separate during shipping.

That being said, sit back and wait. Eventually the pressure exerted by
the cactus growing should loosen something.

Not in the final stage, but it may have been bought from a motorway
services - in which case ...... :-)
--
Jim S