Aye, silica is sand and mica is a form of quartz I think. Might be two entirely different birds me thinks.
ETA ; Research tells me that they are different forms of the same thing at the basic chemical level pretty much and are the primary ingredient in glass. I can only think of using either as a dusting on the surface like sugar beads but my thinker is due for a hundred thousand mile over haul and I have forgotten the place where I last got it done. 
Of course living in Canada I would think having 50 pounds of silica would be very handy for all the ice that hits your world up there.
You might be able to get away with just a dusting on the surface kind of like sugar beads but fifty pounds would take a very long time to use up that way.