148 



bow. Not infrequently one meets Avlth individuals that are broken 

 right off without the parts being severed. Individuals also occur 

 which are partly split lengthwise, one of the parts being bent 

 out from the other like a branch. 



The mode of aggregation of the elpidite individuals seems 

 to be quite irregular. The thicker columns cross one another 

 in various positions; from them thinner needles shoot out in 

 different directions, more or less completely filling the inter- 

 spaces. Such sponge -like masses of elpidite often serve as a 

 substratum for crystals of other minerals which have been formed 

 later, as calcite, polylithionite, leucosphenite, epididymite, albite, 

 etc. In some cases the interspaces are quite filled up with 

 calcite or some other substance. The elpidite itself also forms 

 quite compact and hard masses consisting of extremely fine 

 fibres felted together and generally of a reddish colour. They 

 therefore present a striking resemblance to the so-called 

 «spreustein» from Langesund in Norway. 



Elpidite has been crystallographically investigated by G. 

 Nordens kiöld^). He found the common elpidite columns 

 wholly unfit for angular measurements, owing to the absence of 

 regular terminations and the dullness of the faces in the longi- 

 tudinal zone , which gave no reflections. Only after a long 

 search he succeeded in finding some well -developed crystals, 

 the length and thickness of which he states to be 0,1 — 0,2'^'" and 

 0,03 — 0,05"^"^ respectively. On these crystals, which belong to 

 the rhombic system, he could determine the following funda- 

 mental angles. 



(Oil) : (001) = 44°22' and (llO) : (iTo) = 54° 12'. 



From these measurements were calculated the following 



axial ratios: 



a:h:c = 0,5117 : 1 : 0,9781. 



') Geol. Foren. Förh. Vol. 16, 1894, p. 343. 



