Washington — Catalan Volcanoes and their Roclcs. 231 



tion AbjAiij, forms about one-half of the rock, is subhedral to 

 euhedral, thin tabular, the tables from 0*3 to 0*7 mm long and 

 0*02 to - 05 mra thick, twinned according to the Carlsbad and 

 albite laws, zonal structure not present. The augite, which 

 forms about one-quarter of the rock, is very pale greenish gray, 

 with an extinction angle on 5(010) of 39°. The phenocrysts 

 are subhedral to anhedral, stout prismatic to equant, from 0*5 

 to 2 mm long, running serially down to the abundant small, 

 (0'01 to 0*05 mm ) anhedra of the groundmass. The olivine 

 phenocrysts, slightly larger than the augites, are euhedral to 

 subhedral, the usual domes and pinacoids being present, almost 

 equant, often fragmentary, quite colorless and fresh. There 

 is little or no olivine in the groundmass. Anhedral to subhedral 

 ore grains, from 0*01 to 0"05 mm , are common, scattered uni- 

 formly through the rock. The large amount of TiO„ shown 

 by the analysis indicates that it is highly titaniferous, but noth- 

 ing that could be definitely identified as ilmenite or titanite 

 was seen. Between these constituents there is a small amount 

 of a colorless, distinctly anisotropic base, which may be consid- 

 ered to be probably alkali-feldspar, as the analysis indicates 

 that a considerable quantity of this must be present. The 

 texture is essentially intersertal, characterized by the diver- 

 gently arranged tables of plagiocase, with interstitial granular 

 augite, olivine, and ore. As the augite is not xenomorphic 

 towards the other constituents, and is not poikilitic, the texture 

 cannot be regarded as ophitic in the true sense of this term. 

 The mottled, weathered specimens showed no definite jjeculiar- 

 ities under the microscope which could be connected with this 

 appearance. 



Jlode. — The mode of the specimen from Castellf ullit which 

 was analyzed was estimated by Rosiwal's method, a large num- 

 ber of measurements being made on two sections, with the 

 following results : 



Feldspar 53 -7 



Augite 25-8 



Olivine 10-8 



Ores 8-9 



Apatite 0-8 



100-0 



Chemical composition. — A specimen of the upper, prismatic 

 flow at Castellfullit was analyzed, with the results shown in I 

 of the table of analyses on page 239, which may be regarded as 

 typical of this type. The silica is distinctly higher than in the 

 other rocks of the district, but in other respects it does not 

 differ widely from them. The rather high total oxides of iron. 



