2i6 ALBERT JOHANNSEN 



Loewinson-Lessing^ expressed the opinion that kulaite is the 

 extrusive equivalent of heumite, with which the present writer 

 does not agree. Heumite is described by Brogger^ as a rock essen- 

 tially of soda-orthoclase or soda-microcline with other feldspars, 

 very small amounts of nephelite and sodalite, and considerable 

 barkevikite and biotite. Furthermore, the leucocratic minerals 

 in heumite form only 53 per cent of the rock, and the subordinate 

 plagioclase is oligoclase-albite, and not basic plagioclase. 

 (2324) Nephelite- (leucite-)monzogabbro. A term suggested 

 here for the nephelite- (leucite-)bearing rocks of the basic plagioclase 

 series, and comparable to the granogabbros among those bearing 

 quartz. Nephelite-syenogabbro, suggested previously,^ is with- 

 drawn. See notes under (229) and (2314). 



Essexite Sears is quite variable, but probably belongs 

 here or to (2325), or to both, although the original description by 

 Sears'* does not mention the presence of orthoclase. He says it con- 

 tains augite, hornblende, biotite, plagioclase, and nephelite fi 

 the usual accessories. Washington,^ describing the same re 

 says that it is essentially a basic monzonitic rock in which fek 

 spathoids and both lime-soda and alkali feldspars are present. The 

 feldspar ranges from AbiAui to AbiAuz, and "an alkali-feldspar 

 is not uncommon .... often microperthitic." Nephelite is 

 fairly abundant. In another specimen the plagioclase was AbjAuj 

 and only a few grains of alkali-feldspar were seen. Speaking of 

 certain other rocks described as essexites, Washington^ says that 

 since they contain neither nephelite nor alkali-feldspar, they are not 

 essexites. Many rocks, clearly not essexites, have been described 



' F. Loewinson-Lessing, "Kritische Beitrage zur Systematik der Eruptivgesteine, 

 V," Tscherm. Min. Petr. Mitth., XXI (1902), 322. 



^ W. C. Brogger, Die Eruptivgesteine des Kristianiagebietes. Ill: Das Ganggefolge 

 des Laurdalits (Kristiania, 1898), pp. 98-113. 



3 Albert Johannsen, "Suggestions for a Quantitative Mineralogical Classification 

 of Igneous Rocks," Jour. GeoL, XXV (191 7), 89. 



4 John H. Sears, " Elaeolite-Zircon-Syenites and Associated Granitic Rocks in the 

 Vicinity of Salem, Essex County, Massachusetts," Bull. Essex Inst., XXIII 

 (1891), 146. 



s Henry S. Washington, "The Petrographical Province of Essex County, Massa- 

 chusetts," Jour. GeoL, VII (1899), 53-56. 



* Loc. cit. 



