I observed fine powder-the result of the lava grit spread for friction
As said before, lava is not just lava (it is like beer, maybe). There are all different types around and they are all different. Particle size and melting point seem to be the most relevant factors, but basically knowbody knows for sure, due lack of interest and leck of funding, hence no research.
Indeed so far the only way of dealing with it safely is avoidance.