752 



H. S. WASHINGTON 



These three are all similar in their general features. In C,~it is 

 evident that some of the normative olivine has gone into the biotite. 

 It may be added that the small amount of excess TiO, (represented 

 normatively as perofskite) has been assigned to biotite, the some- 

 what abnormal composition of which is indicated by its optical 

 characters. The large amount of glass is very striking, as well as 

 the general composition which must have been assigned to it in 

 each case had it crystallized. For A and B, it would have about 

 the composition AbiAnj, including a little orthoclase with a small 

 amount of analcite. In C, the 40 per cent would be distributed 

 approximately as follows: orthoclase, 15; andesine (AbjAni), 20; 

 analcite, 5. While the figures given here and in the table are 

 admittedly only rough approximations, yet there can be no doubt 

 that they give an idea of the general order of the. various minerals 

 present. 



TABLE IV 



Analcite . 

 Augite . . 

 Olivine. . 

 Biotite. . 

 Ores. . . . 

 Apatite . 

 Glass. . . 



20 

 12 



IS 

 3 



42 



5 



20 



6 



5 

 18 



2 

 44 



10 



25 

 10 



13 



2 

 40 



A. Mode of analcite basalt. Scano. 



B. Mode of biotite-analcite basalt. Monte Columbargiu. 



C. Mode of analcite basalt. Bonorva. 



Rock name. — ^The name of analcite basalt, first proposed by 

 Lindgren,' is entirely applicable to these rocks, and is preferable to 

 that of monchiquite, which was originally applied to rocks in which 

 the analcite is present in the base or as a glass of the same composi- 

 tion. It is worthy of remark that, had the rock solidified under 

 such conditions as to be holocrystalline, the modes given above 

 show that a very considerable amount of andesine or labradorite 

 would have been present (as has been the case in the Bohemian rock 

 cited above). In this case, the name analcite basanite would have 

 been appropriate. 



^ W. Lindgren, Proc. Cal. Acad. Sci., Ill (1890), 51. 



