Electron paramagnetic resonance and optical absorptions of some natural fluorites correlate with the color of the specimen This led to the identification of the impurity (yo2) responsible for coloration of the red fluorites of Srvitzerland, and to the identification of the probable impurity (Sm2+) responsible for coloration of the green fluorites from Weardale (England) and the Diirrschrennenhdhle (Switzerland).