All these are strikingly alike in appearance and general characters, differing essentially only in chemical composition, and it would seem better to reserve the name cerargyrite for the whole group, using the names chlorargyrite (AgC1), embolite (Ag(Cl, Bl)), bromargyrite (AgBr) and iodembolite (Ag(C1, Br, I)) for the different isomorphous members of the group. They are cubic in crystallization, with the cube and the octahedron as prominent forms, but crystals are small and usually indistinct; there is no cleavage.
Sabatier's theory as to the nature of these documents was, in brief, that the Speculum perfectionis was the first of all the Lives of the saint, written in 1227 by Br.
Leo; on the other hand, Thomas of Celano's two Lives are free from the "tendencies" ascribed to them by Sabatier, and that of 1248 was written with the collaboration of Leo and the other companions; thus the best sources of information are those portions of the Speculum that can with certainty be carried back to Br.
The single gill-plume br lies to the left of the median line in natural position.