Mirorn or Tourmaline was a relatively common mineral found in granites and granites in association with metamorphic rock. Ubain in the east displayed the finest tourmaline, used to aid spells for the healing of horses and other animals. The colours of mirorn could vary but well known was the catseye variant.
- MERP Rulebook 2nd Edition
- The Gems of Middle-earth, online essay by William E Wilson