86 



hardness, both of which were found to agree tolerably well with 

 those of chlorite. On ignition, however, the mineral proved to 

 contain no water, and a complete analysis showed a composi- 

 tion which does not agree with that of chlorite or of any other 

 known mineral. The mineral consequently being a new one, 

 the name sp odioph yllite ^ is proposed for it on account of 

 its colour and structure. 



Spodiophyllite is met with only in crystals. These are bounded, 

 as far as has been hitherto observed, only by the hexagonal 

 prism and the base (Fig. 2, Plate V). Such individuals some- 

 times attain a length of 1 ""^ and a width of 5 — б™"", but the 

 majority of the crystals are much smaller in size. As no 

 pyramidal faces have been observed , the axial ratio cannot, 

 be given. Nor do the ordinary crystals offer any clue by 

 which one cotild come to a decision of the question, whether 

 the mineral belongs to the hexagonal or to the trigonal system. 

 Hovewer, there sometimes occur a sort of embryonic forma- 

 tions of the mineral , of which Fig. 5 gives a diagrammatic 

 representation. They consist of thin trigonal tables , often 

 forming twins with the base as composition face and one 

 individual revolved through 60° round the principal axis. This 

 makes it most likely that the crystals of spodiophylUte belong 

 to the trigonal system. 



Owing to the micaceous cleavage of the mineral parallel 

 to the base the crystal individuals easily break in this direc- 

 tion ; they are, therefore, often terminated by cleavage surfaces. 

 However, several crystals are not broken, but present at their 

 ends real crystal faces. These are highly brilliant and gene- 

 rally perfectly even. Sometimes, however, there occurs on the 

 basal plane a system of striations parallel to the hexagonal 

 outline of this plane (Fig. 2, Plate V). Also lath-like elevations 

 in the same orientation have been observed. 



^) From Znàâtoç, ash-grey, and Фиккоу, leaf. 



