X, A, 5 Pratt: Iron Ore on Calambayanga Island 



Table I. — Analyses of iron ores from Calambayanga Island. 



[Figures give per cent.]' 



329 



Constituent. 



Sample. 



1 



2 



3 



4 



5 



6 



Silica (Si02) 



1.02 



1.31 



97.35 



1.29 

 6.52 



68.28 

 9.22 

 2.77 

 0.29 

 0.09 

 0.10 

 0.12 



54.96 









8.71 



Alumina (AI2O3) 









Ferric oxide (Fe203) _ _ 











Ferrous oxide (FeO) 











Lime (CaO) 













Magnesia (IVIgO) 















0.11 

 0.001 











Phosphorus (P) 



0.001 

 0.138 

 57.11 



0.005 

 0.07 

 63.69 



0.008 

 0.067 

 46.06 



0.035 

 trace 

 65.76 



Sulphur (S) - - -- 



Total iron (Fe) . 



64.14 





1. Calambayanga ore: Average composition of a sample of 200 kilograms (440 pounds) 

 of representative ore from Calambayanga Island. Analysis by T. Dar Juan, chemist. Bureau 

 of Science. 



2. Calambayanga ore : Hand specimen ; analysis by Forrest B. Beyer, formerly chemist. 

 Bureau of Science. 



3. Calambayanga ore : Sample taken by P. R. Fanning, formerly assistant, division 

 of mines. Bureau of Science, representative of many blocks of ore along entire outcrop 

 on Calambayanga Island. Analysis by T. Dar Juan, chemist. Bureau of Science. 



4. Calambayanga ore: Sample taken by P. R. Fanning, formerly assistant, division of 

 mines. Bureau of Science, from many blocks of ore over a distance of 500 meters on main- 

 land near Calambayanga Island. Analysis by T. Dar Juan, chemist. Bureau of Science. 



5. Calambayanga ore : Sample taken by P. R. Fanning, formerly assistant, division of 

 mines. Bureau of Science, on Calambayanga Island from a single lump specimen. Analysis 

 by T. Dar Juan, chemist, Bureau of Science. 



6. Bato-bolani ore : Hand specimen taken by H. M. Ickis, formerly assistant, division 

 of mines. Bureau of Science ; analysis by H. S. Walker, formerly chemist. Bureau of 

 Science. 



to the quartz vein or lode with which it is associated. Veinlets 

 of ore are found in the quartz, and quartz occurs sparingly in 

 the ore. The processes which produced the body of quartz 

 probably yielded under different local conditions the adjacent 

 body of iron ore. Both types of mineralization probably resulted 

 directly or indirectly from the intrusion of dikes into the sedi- 

 mentary rocks near the contact with the older igneous base. 

 Apparently there was some replacement of the wall rocks as 

 well as the filling of cavities and fractures. Probably the lime- 

 stone and the calcareous sediments were most susceptible of 

 replacement in this manner. The dike of gabbro on the north- 

 western shore of the island with its notable proportion of mag- 

 netite may be taken to represent a part of the intrusive rocks. 

 The tuff and agglomerate on the shore of the island and on the 

 neighboring islands and mainland are surface extrusions which 

 may be related genetically to the dike rocks. 



Rinne concluded that the Bato-bolani ore had resulted from 



