380 EaMe — Identity of Palacheite and Botryogen. 



exceedingly small and seldom occurs. Assuming it as |i01}, 

 the vertical parameter for palacheite would become 0*7992, 

 which corresponds to the c-axis of botryogen, calculated by 

 Hockauf from Haidinger's measurements. Most of the crystals 

 are worthless for the determination of the elements, because of 

 striated and vicinal faces ; but the axial elements for palacheite 

 were calculated from the measurements, with the two-circle 

 goniometer, of several very minute crystals which gave good 

 reflections, and it seems probable they are nearer the true values 

 for botryogen than those given by Haidinger. 



The excellent cleavage parallel to the clinopinacoid seems 

 not to have been observed on botryogen. This cleavage is 

 more prominent and better than the prismatic cleavage. Yery 

 little has been done on the optical properties of botryogen. 

 Hockauf states that the plane of the optic axes lies nearly 

 normal to the prismatic faces. As a matter of fact it is nearly 

 parallel to the edge 110^ 110. The analogy of the interfacial 

 angles to those of anorthite, which he mentions, probably 

 means little, as the crystals are undoubtedly monoclinic. 



The crystals remain unchanged in ordinary dry air, as the 

 original specimens, exposed in the laboratory, for over a year, 

 have suffered no alteration. Much yellow earthy sulphate, 

 however, accompaaied the material recently obtained, which 

 may have been derived from the crystals by exposure to damp- 

 ness. This yellow coating has a strong astringent taste, like 

 coquimbite, while the taste of the fresh crystals is barely per- 

 ceptible or none. The yellow coating must be a different sul- 

 phate, although Hockauf states that the analyses of the ochre 

 yellow substance and of the red crystals were essentially the 

 same. 



An unsuccessful attempt was made w^ith a small amount of 

 the original substance to recrystallize the mineral ; with the 

 large amount of material now at hand, further experiments 

 will be made in the hope of obtaining good crystals. The 

 main difficulty is perhaps in keeping the mineral into solution 

 in pure water without the precipitation of the basic sulphate, 

 which so readily forms. 



While the name palacheite should be recalled, although the 

 name botryogen is a misnomer for these crystals, the work 

 will stand as a more complete study of the rare sulphate botry- 

 ogen than has heretofore been possible. 



University of California. • 



