Crusty moles usually happen for one of two reasons. One; it has begun to dry out, or it has become infected. It is very easy to tell the difference between these two situations.
If your mole is drying out it might appear crusty, but it will also be dry. You should not see any leakage of any sort, and there will not usually be a large amount of pain involved. It will also likely fall off at some point and heal over quite nicely. Sometimes using tea tree oil to dry it out for mole removal can result in this appearance. It will also eventually dry up completely and fall off.
If it has become infected you will see pus along with the crusty appearance. It will usually be somewhat more painful to touch, and usually appear red and slightly swollen. It might not heal as well either, and should not fall off on its own. If you look carefully you might also see a break in the skin, but not always. It could be the pores within the skin that have become infected. You will have these normal pores within the skin of your mole.
As you can see there really is not anything at all alike about these two possible crusty moles. They are two very different things, and one might require medical interventions as well. Some simple antibiotic ointments could help with the infection. If it does not get better you should seek advice from a physician or dermatologist.