224 ALBERT JOHANNSEN 



classed by Rosenbusch^ as theralites "ist die Labrador! tmischung 

 die herrschende, nach auszen hin aufsteigend bis zum Andesin, in 

 den Kernen sinkend bis an die Grenze zum Bytownit." The 

 average feldspar, therefore, is basic plagioclase. Olivine may or 

 may not be present. In the rock from Costa Rica described by 

 Wolff and called the true theralite type by Rosenbusch, who 

 named it, the plagioclase is labradorite. The rock contains, 

 however, a little orthoclase, not necessary in the type. 



Kylite Tyrrell,^ with 3 1 per cent labradorite, 4 per cent 

 nephelite, 1.3 per cent analcite, 26 per cent titanaugite, 32 per cent 

 olivine, and small amounts of ilmenite, biotite, and apatite, belongs 

 here also. It is a plutonic rock occurring in the Kyle district of 

 Ayrshire, whence its name. 



Syn. : Olivine- theralite. 

 (3330) No plutonic rock has been located in this family, but a 

 rock described as a pikrit-basalt by QuenseP from Juan Fernandez 

 occurs among the extrusives. It contains 50 per cent or more of 

 olivine. 



CLASS 3, ORDER 4 



(3414) Ricolettaite. The only rock located here is a dark calcic 

 gabbro from Traversellitthal, north cliff of Ricoletta, Monzoni. 

 It consists of orthoclase 5 to 7 per cent, anorthite 35 to 40 per cent, 

 pyroxene 40 per cent, and a little biotite, olivine, and magnetite. 

 It was described by Doelter'' and deserves a new name. 



(3415) Yamaskite Young. This anorthite-augite rock from 

 Mount Yamaska, Quebec, was described by Young.^ A similar 

 rock, but carrying olivine, was described by O'Neill.^ 



Olivine-yamaskite. 



'H. Rosenbusch, op. cit. (4th ed., 1907), p. 413. 



' G. W. Tyrrell, "The Late Palaeozoic Alkaline Igneous Rocks of the West of 

 Scotland," Geol. Mag., IX (1912), 121. 



3 P. D. Quensel, "Der Geologic der Juan Fernandezinseln," Bull. Geol. Inst. 

 Upsala, XI (1912), 265. 



* C. Doelter, "Chemische Zuzammensetzung und Genesis der Monzonitgesteine," 

 Tscherm. Min. Petr. Mitth., XXI (1902), 102. 



5 G. A. Young, " Geology and Petrography of Mount Yamaska, Quebec," Geol. 

 Surv. Canada, Ann. Rept., XVI, Part H (1906), p. 16. 



*J. J. O'Neill, "St. Hilaire (Beloeil) and Rougemont Mountains, Quebec," 



Geol. Surv. Canada, Mem. 43 (Ottawa, 1914), p. 66. 



