Of course, he could have removed the gem so that it wouldn’t damage the ring when it was transfigured back, and put it on the other side of the desk so that when the rock “fell with a loud crack upon the Headmaster’s desk” it wouldn’t smash the ring.
Interesting point.
Of course, he could have removed the gem so that it wouldn’t damage the ring when it was transfigured back, and put it on the other side of the desk so that when the rock “fell with a loud crack upon the Headmaster’s desk” it wouldn’t smash the ring.
But yours is still possible as well.