150 



the exlraordincirily small dimensions of the crystals on which 

 he made his observations. This is especially true with regard 

 to the value from which the c-axis has been calculated. As for 

 the «-axis INordenskiöld himself remarks that, owing to the 

 irregular development of the prismatic zone , it has not been 

 possible to obtain quite accurate values for its angles. 



For the calculation of the axial ratios I have made use of 

 the following angles : 



(110) : (no) = 45° 3' and (031) : (031) = 88^45'. 



The axial ratios calculated from them are 

 а:Ъ:с= 0,51008 : I : 0.97813. 



The following forms have been observed: 

 a = {lOO}, Ъ = {OIO}, с = {OOl}, m = {lio}, 

 ^ = {l20}, c/ = {on}, e = [on}, (/ = {102}. 



All the forms given by Nordenskiöld as certain have 

 been found again by me, with the exception of e. Only one 

 new form have I been able to ascertain, viz. g. 



The common elpidite individuals which are not terminated 

 by crystalline faces are generally bounded in the longitudinal 

 zone by the forms m and n. The faces belonging to the form 

 n are in general predominant. As the angles which these faces 

 make with one another are about the same as those of amphi- 

 bole, the elpidite individuals mostly look like common actinolite 

 columns. On some individuals also the first pinacoid a has 

 been observed, and then the form и is present as an extremely 

 narrow bevelment on the sharp edges of the crystals. 



On perfectly developed crystals also the second pinacoid h 

 is present in the vertical zone (Fig. 2, Plate VIII). This form is 

 much more common on the crystals than a. The faces be- 

 longing to the form n are often larger than those of the form 

 m (Figs. 3, 4, Plate VIII). The faces in the vertical zone are 



