pipe insulation

is there an easy way to tell the difference between mineral wool and glass fibre insulation? I have access to cross sections of what the engineer says are both but they both look the same to me.

Heat it up with a lighter

It's ok to do this and was my first thought also that they would react differently to heat.
Only trouble is I still don't know how to tell the difference. How will each material react when heat is applied?
Thanks,
J

Thanks for the safety considerations. My intention was just to give a clue based on the melting temperature of the materials. Of course it has to be done in a safe manner.

I have been to plant has combustible vapor where I had to surrender my lighter, cell phone at the gate, my car exhaust was fitted with flame arrester and I was issued a explosion proof walkie talkie, emergency response card, etc ... I would not use a lighter in such environment, (beside, I would not have one to use).

Sorry, but that hasn't answered my question. Which material will melt first? I need to be able to tell one from the other.