Is it normal for a molar tooth that had root canal turn black above the crown?

Yes: This is possible. This discoloration will be covered by a crown anyway. See your dentist to complete your treatment.

Normal?: This only happens in a small percentage of cases, but in not uncommon. When the tissues inside the tooth deteriorate, the tooth can stain from within, leaving a darker area exposed. There are cosmetic remedies for this. Discuss your options with your own dentist.