58 



closely approximating to 60° and 120° (Fig. 4, Plate ПИ), Among 

 the present forms, t is always predominant, and the other 

 forms V, s and и occur only as extremely narrow truncations. 

 The second pinacoid Ъ is almost always present, mostly also e 

 and J', the latter, which is new, nearly as often as the 

 чУ~ former. The pinacoid of the first order, q, is represented by 

 large faces. In the zone between it and the third pinacoid 

 с other forms occur, but the faces belonging here were too 

 narrow and too dull to allow of a determination. The zone 

 [310, 001] is of special interest. Of the forms belonging here 

 only I occurs on the Norwegian mineral. On the Greenland 

 mineral not only this form but also the three new ones, z^ k, 

 and г, have been observed and determined on the same corner 

 of the crystal. All of the faces are distinctly developed and 

 allow of good measurements. The form к belongs to the zone 

 q:k :t :b running round the crystal table. This zone is of 

 particular importance, because, next to the third pinacoid (OOl), 

 t is the most dominating form of the crystals, parallel to which 

 there is also a distinct cleavage. One might, therefore, feel 

 inclined to give the crystals such a position that the said zone 

 becomes the vertical zone. The form q would then become the 

 first pinacoid and к and t prisms of the third order. But it appears 

 that, when such a fundamental position is chosen, the other 

 forms have still more complicated symbols than those that 

 result from the position proposed by Brögger. 



All forms whose presence on eudidymite has been hitherto 

 ascertained have been collected together in the following table, 

 which also shows the forms occurring on crystals from the 

 different localities. 



') The form p = {053} is here erroneously designed g. 



