119 



surfaces of a (ЮО) for yellow light 



1H^= 93°. 

 From which we get, if ß (after Funk) is 1-5660 



2P^== 90° 20'; 2 Fa = 89° 40'. 



Thus this elpidite is very nearly optically negative. 

 Generally this needle-shaped elpidite is found completely 

 unconnected with other minerals; only in a single case the 

 needles have been found penetrating rhodochrosite and natrolite. 



Neptunite. 



The material of this mineral collected by Bernburg's ex- 

 peditions is very slight, when compared with what has previously 

 been collected; but with regard to crystallography it is very 

 interesting, as it does not belong to any of the previously known 

 types of the mineral^), but to two new, well characterised types. 



One of these has lately been described by A. Wallenström ^), 

 and consists of quite small crystals lengthily prismatic, and at 

 the ends bounded mostly by e (20l}. According to kind in- 

 formations from Flink, these crystals 

 have come from Bernburg's collec- 

 tion. The crystals I have examined 

 are of rather considerable size, (up 

 to 2 cm); they are developed as 

 shown in fig. 10; they are often 

 flattened after c{00l}, often about 

 isodiametric. Sometimes they are 

 exclusively bounded by c{00l} and 

 w{ll0}; generally, however, small 

 faces are found of s (ill}, о {ill), 



Fig. 10. Neptunite; 



Narsarsuk. 



1) Described by Flink: Geol. Foren. Förh Stockholm, 15, 1893, pp. 196 

 and 467, and Zeitschr. f. Kryst. 23, 1894, p. 346; by Sjöström: Geol. 

 Foren. Förh. Stockholm, 15, 1893, p. 393; by G. Nordenskiold : ibid. 

 16, 1894, p. 346, and by Flink: M. о. G. 24, 1901, p. 120. 



'-') Geol. Forée. Förh. Stockholm, 27, 1905, p. 149. 



