152 NEW YORK STATE MUSEUM 



the magnetite. The latter being commonly in excess constitutes the 



ground mass through which the ilmenite is more or less regularly 



distributed in grains of fairly even size. 



A partial separation of the magnetite and ilmenite was obtained 



with the ore from the Sanford pit at Lake Sanford. A sample was 



crushed through a 40 mesh sieve and the magnetite removed with 



a small hand magnet. The results from chemical analysis of the 



crude ore (1), magnetite concentrate (2) and the ilmenite and other 



residual minerals (3) are given herewith. The analyses were made 



by E. W. Morley. 



1 2 3 



Fe A 55-9 54-39 14-28 



FeO 27.5 28.66 30.93 



Ti0 2 14 8.93 45.23 



It will be observed that the magnetite concentrate still contains 

 a considerable proportion of titanium, mostly due, no doubt, to 

 the inclusion of particles of mixed character. By crushing still 

 finer a cleaner separation may be made, as has been demonstrated 

 for the same ore in recent experiments that are described on a sub- 

 sequent page. The analyses are not reducible to simple terms of 

 magnetite and ilmenite, and further work is needed before the chem- 

 ical relations can be fully stated. It is quite likely that the mag- 

 netite itself carries a proportion of the titanium, in which case the 

 entire removal of the latter would be impossible. 



The remaining minerals found in the titaniferous ores include 

 plagioclase, pyroxene, hornblende, biotite, olivine, garnet, pyrite, 

 apatite, spinel and quartz. The plagioclase is usually labradorite 

 or an allied variety. Both orthorhombic and monocline pyroxenes 

 are represented. Olivine is rather rare in the Adirondack ores so- 

 far as observed. Pyrite is a fluctuating constituent, more abundant 

 in the ores that are included by gabbro than in those found within 

 anorthosite. Spinel has not been certainly identified, but its pres- 

 ence is strongly indicated by the analyses which show an excess of 

 A1 2 3 over the amounts required for the silicates. The analyses of 

 concentrates on page 154 are suggestive also in that connection. 

 Apatite is present in minute quantities only, and the ores are con- 

 sequently low in phosphorus. 



The order of crystallization of the minerals revealed by study of 

 the etched surfaces is as follows: 1, silicates; 2, pyrite; 3, ilmenite 

 and magnetite. 



The order is thus the reverse of the normal one for igneous rocks 

 in which the silicates predominate over the iron ores. The expla- 



