ORIGINAL: Sport_Pilot
Dust is normally a ''soft'' particulate that deforms under pressure. e.g. it is mostly organic.
The dust off your asphalt or concrete or grass strip is mostly clay or sand. Much worse than a few microscopic particles of aluminum.
Normally it's not.
Clay, sand etc. is fairly heavy relatively speaking. Unless you are flying in a dust storm these things are not flying around.
Most dust consists of cast off cells from plants, people, pollen etc. and relatively light particles that can be carried by low speed air movements.
Of course in a higher wind all bets are off, but most pilots tend to fly in relatively dust free ( the visible variety ) conditions or if not put some sort of filter on their intakes.
The particles of aluminum found at the bottom of a crankcase produces a sludge that can contain particles large enough to create a sandpapery feel. This may mean the particles are larger than sand. Not exactly micro particles.
My worry is those macro particles do damage.
Even the micro aluminum particles can not be all that good for the engine though.