Sand v Volcanic particles
Sand is abrasive with a melting point above the temperatures found in a gas turbine engine.
Volcanic particles are abrasive and melt at temperatures lower than in a gas turbine engine.
Sand passes through - the other stuff melts and re-solidifies inside the engine.
Whilst is is undesirable to fly through either of these conditions, it would appear that sand is the least damaging - to engines at least.
p.s.
The particles in the photo in #889 are what I reported seeing on my otherwise clean windscreen last evening.
Last edited by TRC; 18th April 2010 at 09:19.
Reason: Added p.s.