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.