Sans's sockets widen in shock as the flame streaks into Greg's gem. Can a soul be hurt? Can it be destroyed? He doesn't know how these things work here, or how dangerous the flame is - he's just suddenly filled with dread at the idea that he might be about to watch Greg shatter-

-and as the gem tumbles, he reaches out for it, managing to break through Blanche's magical dampening just enough to open a small portal from the air to inside of his closed palm. One moment the gem is about to fall, and the next its smooth surface is burning against the inside of his skeletal fingers.

It's still there. It's still in one piece.