207 



lath-shaped individuals which are plentifully scattered about in 

 the mass and sometimes show twinning. The extinction forms 

 an angle of some few degrees on the length of the laths. 



The minerals just described belong most nearly to the 

 ground-mass against which they only stand out in polarized light. 

 This is, moreover, very weakly doubly refractive; I am inclined 

 to think that also the main mass of it is formed of the minerals 

 mentioned, which only appear, however, when unusually pure 

 and free from inclusions. Whether, and to what extent nephe- 

 line occurs in the rock I have not been able to ascertain with 

 certainty. An attempt to etch the rock with cold hydrochloric 

 acid showed, unexpectedly enough, little effect; no strong gelatine 

 formation could be observed. 



Miss Naima Sahlbom, who has analyzed this rock, found 

 it to be constituted as follows: 



SiO.^ 4443 per cent 



TiO. 1-40 — 



AKO^ 17-89 — 



Fe,0^ 4-00 — 



FeO 4-94 — 



MnO traces 



CaO 12-601) — 



MgO 2-40 — 



K^O 3-02 — 



Na^O 2-55 — 



Loss at ignition 6-25^) — 



99-48 per cent 



') I have not had an opportunity of comparing these flgures with the 

 original analysis journal. In the copy I made myself the flgures run 

 CaO 2-40 "\>, and MgO 12G0 "/o. But it seems very probable that 

 there is some mistake in the latter figures and that the result should 

 be as given above. 



-) From this Яз*^. determined according to Penfield's method, 5" 16 "lo, 

 remainder 109 "/<•, presumably COg. 



