gsminmag Mineralogical Magazine Mineralogical Magazine 0026-461X Mineralogical Society 10.1180/minmag.1934.023.146.01 The form Relations of the Lead Oxychlorides, Laurionite, Paralaurionite, and Fiedlerite Palache Charles 1 Professor of Mineralogy, Harvard University, Cambridge, Massachusetts

The author desires to acknowledge his indebtedness to his co-workers in this study. Dr. L. LaForge made the preliminary studies and calculated some of the tables. Dr. M. A. Peacock made some of the measurements and all of the drawings. Mr. H. Berman determined the optical properties of all three of the minerals.

 9 1934 23 146 573 586 Copyright © 1934, The Mineralogical Society 1934 Summary

New observations on laurionite, paralaurionite, and fiedlerite are presented. The separate identity of each of the first two minerals is confirmed and their homeomorphism is exhibited by a reorientation of laurionite. The form series of fiedlerite has been simplified by the choice of a new unit form. New forms are described on all three minerals. The crystallography of all three species is summarized in new angle-tables and their habits are illustrated by a series of drawings.