Dislocations and fault surfaces in natural apatite

The grown-in defects in gem quality crystals of natural apatite have been investigated using X-ray diffraction topography. The most common defects are the fault surfaces which are parallel to {101} growth horizons, and these fault surfaces result from the incorporation of impurities during the growth of the crystal. The dislocation density of the crystals is low. A majority of these dislocations align with [0001] and have Burgers vector b = c[0001]. Some dislocations make about 15° with [0001] and have a Burgers vector with a c-axis component, probably b = a + c<123 >. A minority of the dislocations, nearly normal to the growth surfaces, have a mixed character with Burgers vector b = a<110>.