WRIGHT-FHNNERj PETBOGBAPHIC STUDY 81 



for one-half hour, was found to have been melted to a dark greenish- 

 brown mass in which remnants of the original plagioclase and quartz 

 fragments were still visible under the microscope. Some glass was 

 still present but it had largely crystallized to a substance which 

 agreed with pyroxene in its optical properties, so far as these could 

 be ascertained. Fine specks of iron oxide were noted frequently in 

 the section. 



Fragments of the scoriae 263746 heated to 1,000° for 30 minutes 

 exhibited a slight change in color but were not profoundly altered. 

 Held at 1,100° for 30 minutes the mass had sintered together and 

 the change was more noticeable. Heated at 1,150° for 3| hours, the 

 material was completely fused to a dark brownish-green, vesicular 

 glass which still contained numerous fragments of the original min- 

 erals. Acicular microlites resembling pyroxene in optical proper- 

 ties were abundant; also iron oxide particles. The refractive index 

 of the glass was unusually high, ranging from 1.55 to 1.59. It is of 

 interest to note that in all these heating experiments the minerals 

 which crystallize out of the melt are not those which appear in frag- 

 mental state in the glass and wliich were present in the original 

 material that was subjected to the heat treatment. The same holds 

 true of the fragmental mineral grains in the scoriae from Miramar 

 and Alvear. 



5.491 

 57.O0I 



27.981 



8.73 

 0.62J 



62.49 



57.33 



