Cathodoluminescence image of intrasectoral zoning in apatite.

Cathodoluminescence image of a three-sided growth hillock on a prism (100) face of an apatite crystal from the Golconda mine, Minas Gerais, Brazil. Luminescence is activated by different rare earth elements. The luminescence zoning, intrasectoral zoning, is the result of segregation of different rare earths among the symmetrically nonequivalent vicinal faces of the hillock and differential incorporation during growth of the crystal. John Rakovan photo. Modified from Rakovan, J., and Reeder, R.J. (1994) American Mineralogist, 79, 892-903.