Handgathered marbles can be opaque also. They usually always exhibit the 9 or looping form though. They are basicaaly the same as the later handgathered slags and opaques(oxbloods, Akros MFCs ect) just rounded by hand not on a machine. and with the process being slower the rougher cutoffs were usually ground smooth for better final results. And yes they are usually very smooth on the nine side(bottom) of the marble. Peace,Galen