CLASSIFICATION OF IGNEOUS ROCKS 219. 



from Knox County, Maine, described by Bastin.^ They are 

 melanocratic orthogranites. 



(317) Mela-albite-granite. A poor name, which should be 

 replaced owing to the former use of albite-granite for a different 

 kind of rock. See note under (217). 



(318) Mela-albite-adamellite. See note under (218). 



(319) Mela-albite-granodiorite. See note under (219). 



(3 1 10) Mela-albite-tonalite. See note under (2 no). 



(3111) Mela-orthosyenite. See note under (2 in). 



(3112) Mela-albite-syenite. See note under (2 11 2). 



(3113) Mela-albite-monzonite. See note under (2 113). 



(3114) Mela-albite-monzodiorite. See note under (2 114). 



(3 1 1 5) Mela-albite-diorite. See note under (2 11 5). 



(3 1 1 6) Orthoshonkinite. Weed and Pirsson^ gave the name 

 shonkinite (from Shonkin, the Indian name for the Highwood 

 Mountains, Montana) to a melanocratic "granular plutonic rock 



consisting of essential augite and orthoclase It may be 



with or without olivine, and accessory nepheline, sodalite, etcetra, 

 may be present in small quantities." In another place^ they 

 state that "a trichnic striated feldspar is also present, but in no 



considerable amount Itisalbite." The amount of albite is 



not mentioned, but it is included in the estimated amount of alkali- 

 feldspar. Based on the definition, however, no albite is necessary, 

 and by analogy with other rocks (see under (in)) the term ortho- 

 shonkinite may be applied to the rocks as defined with less than 

 5 per cent albite. Where the albite percentage is greater, the rock 

 falls into Family 17 as albite-shonkinite or shonkinite simply. 

 While the original rock contained traces of feldspathoids, by defini- 

 tion none is necessary, and none is shown in the mode of this rock 

 as given by Washington.'' It has, however, affinities with the 

 nephelite rocks; consequently, though it may fall on the feldspar 

 base line of the double triangle, it is to be classed with the 



' Edson S. Bastin, "Some Unusual Rocks from Maine," Jour. Geol., XIV (1906), 

 173-80. 



^Walter H. Weed and Louis V. Pirsson, "Highwood ilountains of Montana," 

 Bidl. Geol. Soc. Amer., VI (1895), 415-16. 



3 Ibid., p. 412. 



^ Henr)^ S. Washington, "The Foyaite-IjoHte Series of ]Magnet Cove: A Chemical 

 Study in Differentiation," Jour. Geol., IX (1901), 613. 



