220 ALBERT JOHANNSEN 



feldspathoid rocks in Family i6. Furthermore, a modal analysis of 



another rock' shows alkali-feldspar 20 per cent, nephelite 5 per cent, 



sodalite i per cent, apatite 4 per cent, and mafites 70 per cent (10 of 



which is olivine). The latter rock, consequently, may be called 



a nephelite-shonkinite of Family 21. 



(3 1 1 7) Shonkinite. This is albite-bearing shonkinite. See 



note under (3 11 6). 



(3 1 21) Nephelite-shonkinite. See note under (3 11 6). 



(3124) Melalitchfieldite. See note under (2124). 



(3125) Melamariupolite. See note under (2125). 



(3 131) Bekinkinite Rosenbusch and Missouri te Weed and 



PiRSSON. 



The melanocratic nephelite plutonic rock of this family is repre- 

 sented by bekinkinite, named by Rosenbusch^ from its occurrence 

 on Mount Bekinkina on the peninsula Ambavatoby, as described by 

 Lacroix.^ While the original rock is said to contain a small amount 

 of anorthoelase, the definition of the type rock of Rosenbusch does 

 not require it. He calls it a plutonic form of nephelite basalt, 

 and says it is related to ijolite as missourite is to fergusite. 



Missourite was named by Weed and Pirsson'* from its occurrence 

 on the Missouri River. It is a melanocratic, feldspar-free leucite 

 rock. It contains 16 per cent leucite, 8 per cent analcite and 

 zeolites, 50 per cent augite, 6 per cent biotite, and 5 per cent iron ore. 



Farrisite Brogger^ is a melanocratic melilite rock of 

 this family. 



Mela-nephelite-basalt is the extrusive equivalent of 



bekinite, mela-leucite-basalt of missourite, and mela-melihte- 



' Louis V. Pirsson, "Petrography and Geology of the Igneous Rocks of the High- 

 wood Mountains, Montana," U.S. Geol. Surv., Bull. 237 (1905), p. 104. 



^ H. Rosenbusch, Mikroskopische Physiographic der massigen Gesteine (4th ed.; 

 Stuttgart, 1907), p. 441. 



3 A. Lacroix, "Sur quelques roches ijolithiques du Kilima-Ndjaro," Bull. Soc. 

 Min. France, XXIX (1906), 90. 



-» Walter H. Weed and Louis V. Pirsson, "Missourite, a New Leucite Rock from 

 the Highwood Mountains of Montana," Amer. Jour. Sci., II (1896), 323; Louis V. 

 Pirsson, "Petrography and Geology of the Igneous Rocks of the Highwood Mountains, 

 Montana," U.S. Geol. Surv., Bull. 237 (1905), p. 118. 



sW. C. Brogger, Die Eruptivgesteine des Kristianiagehietes . Ill: Das Gang- 

 gefolgschaft des Laurdalits (Kristiania, 1898), p. 70. 



