34 



I'KNTTI K.SKOLA. 



M.-N. Kl. 



] 00.29 



101.66 



From 58 g of ground rock was obtained i g iron ore and rutile 

 which sank in a solution of sp.g. 4.13. This quantit}' was treated with 

 hydrofluoric and sulphuric acids whereby the iron ore was dissolved and 

 rutile alone was left. In the ore I found 36 '^/0 TiO.,, but no chromium. 

 Assuming it to be il m e n i te-m agn eti te, I calculated the following com- 

 position : 



TiO., 36 0/0 



FeO 41 „ 



Fc.Og 23 „ 



That portion whose specific gravity was less than 3.35 contained 

 apatite and a m y r ni e k i t e-1 i k e i n t e r g r o w t h of p }■ r o x e n e and 

 plagioclase. By boiling with nitric acid, 50^/0 of it was dissolved and 

 considered as apatite, seen in large amounts under the microscope. This 

 apatite was found to contain 0.27 ^Vo CI. Assuming that only chlorine- 

 apatite and fluorine-apatite take part in its composition this apatite should 

 contain nearly 95 ^/0 fluorine-apatite. 



The quantitative mineral composition, or mode, arrived at by the 

 mechanical analysis is given in the following table where, as an example 

 <1f*the method, the whole calculation of the bulk composition of the rock 

 from the mode and the analyses of the minerals is quoted. 



1 Inclusive 5.7 ^0 pyroxene-plagioclase-myrmekite. 



