82 BUKEAU OF AMERICAN ETHNOLOGY [bull. 52 



Ratios 



rn Sal 62.49 ^5 J ^t ttt 



^^^^^ SW = 37733>3<1--- "-^" 



Order Q = -M9^<1 5 



Urder ^ 57.00^7 ^ 



c ^ K,0' .021 3^ 1 



Subrang ^^_^=_^ <_ >^.. . _. 4 



I. Scoria. North of Necochea. J. G. Fairchild, United States 



Geological Survey, analyst. 

 la. Molecular f)roportions of I. 



This analysis places the rock on the border between Class II and 

 Class III of the quantitative classification. In the Tables of Chemical 

 Analyses of Igneous Rocks, by Washington, rocks ranging from sye- 

 nite and trachyte to diorite and andesite and even basalt are included 

 in the subrang in which tliis analysis faUs. Characteristic of the 

 analysis is the high percentage of ferrous oxide and of titanic oxide. 



SPECIMENS FROM MONTE HERMOSO 



No. 263705. Specimen label. ^ ^ Locality : Monte Hermoso near 

 the old lighthouse. Material: Red loess-sand of the Monte Hermoso 

 formation Jrom the lower hench just above high tide." 



A light-reddish, earthy material, in part indurated and stony, in 

 part loose and friable. Under the microscope the stony part is seen 

 to be composed almost entirely of microscopic calcite grains and 

 clusters usually stained with iron oxide. The earthy, loose part con- 

 sists largely of cryptocrystalline, argillaceous material. Dissemi- 

 nated through the rock are quartz and plagioclase fragments, and 

 some glass, pyroxene, hornblende, biotite, and magnetite. The 

 calcareous portion of this specimen is evidently concretionary in 

 origin. On immersion in water this earth crumbles to a lumpy mud. 

 It gives strong chloride reaction when tested with silver nitrate 

 solution. 



A small quantity of the earth was mixed with graphite and heated 

 to 1,300° for a short time, after which the temperature was dropped 

 to 1,100° and held there over night (16 hours). The resulting mass 

 was found to have been completely fused, no trace of the original 

 material being visible, and to have largely recrystallized. Pyroxene 

 crystals predominated, in lath-shaped prisms, and exhibited the usual 

 optical characteristics: refractive index about 1.66, birefringence, 

 fairly strong, extinction angle c: c usuall}^ high ; the square-end sec- 

 tion of the prisms extinguished along the diagonals. A colorless 



