134 Mr HAIDINGER'S Mimralogical Account of 



In some of the cavities of the same specimen there were, how- 

 ever, crystals in the form of acute four-sided pyramids, similar 

 to Fig. 19, which did not agree" with the symmetry of tessular 

 forms. They were rough, and possessed little lustre, so that 

 they afforded only indistinct measurements of about 140 for the 

 base of the pyramid. . Certain varieties from Wunsiedel, in Bay- 

 reuth, in the cabinet of Mr ALLAN, engaged in heavy-spar, and 

 associated with pyrolusite in very delicate columnar composition, 

 possess the form of Figs. 18, 20. and 23. The two first of these 

 I also observed in a specimen, procured from Mr HEULAND, in 

 the collection of Mr FERGUSON of Raith, having the following 

 ticket : " Hydrous oxide of manganese, in the form of an octahe- 

 dron, with a square basis. Thuringia is extinct" As HAUY'S 

 works contain the pyramidal manganese-ore of MOHS, under the 

 denomination of Manganese oxide hydrate *, this specimen is pro- 

 bably intended for a variety of that species, which, however, is 

 very inaccurately described by HAUY, who united under one 

 head the physical properties of one species with the physical and 

 chemical properties of two or three others, to form a general 

 description, to which no object in nature corresponds. I had 

 long ago observed crystals of the form Fig. 22. engaged in a spe- 

 cimen of the epidote manganesifere of HAUY, in the cabinet of 

 Mr ALLAN, but which I believed likewise to be a variety of Haus- 

 mannite. Upon measurement, however, for which the small 

 but beautifully formed and bright crystals of this variety are 

 better suited than any of the rest, these also turned out to be- 

 long to a species different from the pyramidal one formerly de- 

 scribed. The angles which these crystals afforded are given above 

 as the dimensions of the species. The results obtained from the 

 remaining varieties are not sufficiently consistent to be consi- 

 dered different from these, and as, moreover, the colour of their 



* Traits, 2de ed. t. iv. p. 264. 



