Most dictionaries and people agree that a "bead" is a SMALL object with a central hole or holes which makes it suitable for stringing. If the hole is offset, the object is a pendant. If such an item is too heavy to be worn comfortably, it likely did not serve as an adornment but some other function. Of course, there are the huge beads worn by elephants in Asia so one has to also consider the size of the wearer when one debates whether a perforated object may be considered a "bead."