57 



tion of the largest cleavage, which has exactly the same direc- 

 tion ; but this supposition is contradicted, partly by the fact that 

 this cleavage is not especially marked, so that any mechanical 

 action whatever might split the crystal in other directions also, 

 and partly by the crystals projecting quite freely in a cavity, so 

 that they may not easily have been exposed to any mechanical 

 influence. Whether the sides of the furrow are formed by par- 

 ticular crystallic faces cannot be decided on account of the 

 smallness. in some cavities all, or almost all the crystals are 

 provided with this furrow, in others no single one is found. 

 In a few of the larger crystals of other types several parallel 

 furrows may be seen; but commonly they are far from being 

 so conspicuous. 



The crystals of this type, as before mentioned, are always only 

 of small size ; the length varies between 1 and 4""™, and the breadth 

 between Vs and 2°"°. In larger crystals the form is always some- 

 what varying, and passes gradually into the other types. 



Type II 



is very little deviating from the preceding 

 one; it is especially characteristic by the 

 fact that *t'{30l} is always far predominant 

 over most of the other faces, i^{l01/ 

 is smaller to a corresponding degree, and 

 o{lll}, /"{oil}, and 4021} are very small, 

 or sometimes wanting; especially e{02l} 

 is often wanting. The structure of the 

 faces of the prismatic zone is as in the 

 preceding type. 



As to size and nature in general this 

 form is not different from the preceding 

 one ; it has only been found in a single 

 piece, and the accompanying combination Fig- 3- llvaite, type IL 

 of minerals deviated in no respects from the common one. 



