CLASSIFICATION OF IGNEOUS ROCKS 217 



under this name. The original rock is apparently of Class 2 

 (though some recently described essexites are of Class 3), and 

 certainly of Order 3. 



(2325) Nephelite-(leucite-)gabbro. Rouvillite O'Neill belongs 

 here. This is a rock from St. Hillaire, Quebec, described by 

 O'Neill.^ It may be called a nephelite-gabbro or light-colored 

 theralite. Rosiwal measurements show the rock to consist of 

 nephelite 29.35 P^^ cent, plagioclase (AbsoAnjo to AbjoAngo) 55.9 per 

 cent, apatite 1.15 per cent, pyroxene 7.50 per cent, and horn- 

 blende 3 . 64 per cent. 



(2327) Heronite Coleman. While this is an analcite dike 

 rock, and far from the center point of the family, it is the only rock 

 so far located in this pigeonhole. The name was given by Coleman* 

 to a rock from Heron Lake, north of Lake Superior, consisting of 

 much analcite (53 per cent of the leucocratic minerals), orthoclase 

 (28. 24 per cent), labradorite (13 per cent), aegirite (4.04 per cent), 

 c 7-4/ixiji,onite and calcite. 



30) Lugarite Tyrrell^ is a porphyritic rock, occurring in 

 A^es and as a sill in the Lugar teschenite-picrite complex in the 

 west of Scotland. It consists of analcite (with some nephelite) 

 50 per cent, labradorite 10 per cent, apatite 2 per cent, titanaugite 

 20 per cent, barkevikite 15 per cent, and ilmenite 3 per cent. 

 Tyrrell considers the analcite "original, displacing nephelite." 



CLASS 2, ORDER 4 



(247) Anorthite-granite. 



(248) Anorthite-adamellite. 



(249) Anorthite-granogabbro. 

 (2410) Quartz-anorthite-gabbro. 



(2412) Anorthite-syenite. A syenite whose small percentage of 

 plagioclase is anorthite may be called anorthite-syenite. Here 

 belongs a so-called shonkinite from Elkhorn, Montana, described 



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

 Geol. Surv. Canada, Mem. jj (Ottawa, 1914), p. 35. 



* A. P. Coleman, "A New Analcite Rock from Lake Superior," Jour. Geol., VII 

 (1899), 435. 



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

 Scotland," Geol. Mag., IX (191 2), 77-78. 



