Mirond or Zircon was a common mineral in all types of igneous rocks throughout Middle-earth. Gems were normally found as rounded grains in stream and beach sands, often with mal deposits. Mithgîn and other precious metals were typically melted in crucibles made of zircon.The colours of Zircon could vary but red was most valued.
- MERP Rulebook 2nd Edition
- The Gems of Middle-earth, online essay by William E Wilson