176 



The ajîatite crystals of the second type have been found 

 only at the locality No. 5. The mineral occurred here very 

 sparingly and , as mentioned before , closely associated with 

 aegirine. Other accompanying minerals are zircon (of type III, 

 violet fluorite, albite (in crystals elongated in the direction of 

 the vertical axis) , etc. The aegirine is here older than the 

 apatite, but the fluorite is younger. 



Type Ilf. 



A feature common to the first and the second type of 

 apatite crystals is that they are bounded only by the faces 

 of the vertical zone and the base. On the crystals of the third 

 type, on the other hand, there also occur pyramidal forms. 

 Only a single specimen with a couple of crystals of this kind 

 has been found. The crystals are short prismatic , 8"" in 

 length and of about the same thickness. They are rather well 

 developed with tolerably even and bright faces and consequently 

 well suited for angular measurements with the reflection-gonio- 

 meter. The following forms have been determined : 



m = {l0J0], a:={ll20}, c={000l}, ж = {10П}, s = {n2l}. 



Among the forms of the vertical zone the faces belonging 

 to the prism of the first order, m, are generally broader than 

 those belonging to the prism of the second order, a (Fig. 8, 

 Plate Vlll). The faces of the former kind are also, as a rule, 

 more brilliant than the latter. On the latter there occurs a 

 close vertical striation, which causes them to look almost dull. 

 The basal faces are fairly bright, but not quite even. They 

 are divided into (mostly triangular) fields , which do not quite 

 form a single plane, but incline towards one another at angles 

 that deviate a little from 180°. It looks as if the crystals were 

 built up of a number of trigonal prisms in a position not quite 

 parallel with reference to one another. Of such a polysynthetic 

 structure there is, however, no indication in the vertical zone, 



