262 



The Philippine Journal of Science 



1916 



shale especially has diminished in the section at Tabubunga, a 

 condition which is due probably to the varying overlap of its 

 beds on the basal rocks. 



CHARACTER OF THE PETROLEUM AND RESIDUAL BITUIVIENS 



Natural bitumens are generally conceded to have their origin 

 in petroleum and to consist of various hydrocarbon residuals, 

 left upon the evaporation or dissipation of the more volatile 

 constituents of petroleum. Definite mineral names have been 

 applied to a number of natural bitumens of different character, 

 and this mineral classification is assumed to be complete. But 

 in attempting to classify the various bitumens in Leyte as one or 

 another £>t the recognized bitumen minerals, I find that the de- 

 scriptions of none of the several types apply exactly. If the 

 facts that petroleums vary widely in character and that the 

 residuums from each petroleum form a continuous series from 

 petroleum at one end to a metamorphic product similar to coal 

 at the other end are considered, the difficulty of placing all the 

 possible residual bitumens in a half-dozen classes will be ap- 

 parent. Yet it is obviously not desirable to consider each 

 natural bitumen as a distinct mineral species and to give it a 

 separate name. Consequently I have applied only the broad 

 term natural bitumen to the petroleum residuals in Leyte. 



The following table contains data as to the physical properties 

 of the three principal types of natural bitumens found in Leyte : 

 namely, (1) the material from outcrops A and B; (2) material 

 from outcrop D; and (3) material from outcrops E, F, and G. 

 The bitumen in the mixture at L and M resembles that from 

 E, F, and G, while the bituminous cement in the limestone and 

 at N is similar to the material in outcrop D. 



Table III. — Physical properties of natural bitumens from Villaba, Leyte. 



Property. 



Outcrop. 



A and B. 



D. 



■< 



E, F. and G. 



Specific gravity 



Hardness 



Color 



1.05 



1.016 - - 



0. 98-1. 02. 



1.5. 



Brownish black. 



2.00 



Jet black 



Black 



— - 



Streak 



Luster 



Structure 



Fracture 



Flows 



Black 





Light brown. 



Brilliant - ' - -. 





Dull. 



Schistose. 

 Irregular schistose. 

 At 75° C. 



Columnar 



Viscous 



Conchoidal 





Intumesces, softens, and 

 flows imperfectly at 

 150° C. 



At35°C- 







