Abstract
After an introduction with a few historical comments the writer deals with the matter of nomenclature (illustrated by apatite), including brief remarks on the use of the word isomorphism. The pegmatite phosphates are then discussed in terms of 70 species, presented in four tables showing their chemical compositions; the separation into four tables is based on quasi-genetic grounds. Following remarks concerned with crystal structure and crystal chemistry of the mineral phosphates, the paper is concluded with a section giving data in tabular form showing the present status of x-ray studies of the pegmatite phosphates, both single crystal and powder diffraction; the latter is illustrated with 60 photographs. A final Table 8 serves as an alphabetical index to Tables 2 to 7.
