Tungsten and glass do not make a good combination. A high density object (basically, how heavy an item is for a given volume) gathers more kinetic energy in movement, and dissipates it upon impact, than a light one [cue smashing glass sounds].

While there’s a couple of different methods to work around this problem we employ the easiest one here by making the tungsten particles small. While the density of the whole remains just as high when put in motion each particle’s movement is slightly different, canceling a lot of the momentum and lessening the amount of energy discharged when it hits the wall. This way you can shake it much more vigorously without fear of breaking the glass than if it were a single chunk of tungsten.