> My interpretation of hollow crystals is that the crystals are growing too fast.
This is indeed true and a well known effect observed also in mineral crystals, namely that the edges grow fastest and the faces fail to fill (or the crystals are filled with disordered material. The examples are the mineral crystals of 'Fensterquarz' (window quartz) where only a skeleton of edges is formed, or similar nested 'frames' of Bi. http://www.youtube.com/watch?v=giNEaeloXac http://www.moe-joe-working.com/Moe-Joe-Cell/images/bismuth-crystal-2.jpg BR
