In article .com,
says...
Angle grinder discs have the cutting particles resin bonded onto a
fibre re-enforced pad the particles and resin are different on stone
and metal discs. As a disc is used the cutting particles break
off,often seen as a fine dust, as they break away they expose the next
layer of particles and so on. using the incorrect disc will cause the
cutting edge to clog so reducing efficiency this will also lead to
overheating which can, and does, lead to a condition known as bursting
which is self explanetary, allways use the correct disc for the job in
hand, if you have discs that you can't identify throw them away, i have
experienced a disc disintgrate and at the speeds involved it almost
puts you off using one again, i would also recommend covering up any
exposed skin just incase!


Exactly !!

The difference is in the abrasive particles.

Stone cutting discs are also recommended for the cutting of aluminium
--
Paul Mc Cann