A QUANTITATIVE MINERALOGICAL CLASSIFICATION 

 OF IGNEOUS ROCKS— REVISED 



ALBERT JOHANNSEN 



University of Chicago 



PART III 

 CLASS 2, ORDER 3 



(237) Calcigranite. No plu tonic rock falling near the center 

 point of this family has yet been located. 



Quartz-ciminite. Among the extrusives the only rock 

 found in this family is a quartz-bearing ciminite described by 

 Washington/ Ciminite, named from its occurrence on Monti 

 Cimini, Italy, was defined^ as consisting of alkali feldspar, basic 

 plagioclase, augite, and olivine, with accessory magnetite and 

 apatite. From two modal analyses given, it appears that there 

 are quartz-bearing and quartz-free cimini tes; consequently the 

 two divisions, quartz-ciminite and ciminite, are here made. A 

 modal analysis of one rock, here called quartz-ciminite, gives 

 orthoclase (OrgAbi) 43.6 per cent, labradorite (AbiAuz) 16. i per 

 cent, quartz 4 . 6 per cent, apatite o . 7 per cent, augite 22.4 per cent, 

 olivine 1 1 . 7 per cent, and magnetite o . 9 per cent. Since this 

 rock contains olivine, it is not representative of the normal extru- 

 sives of the family. 



(238) Calciadamellite. This is a quartz-monzonite whose 

 plagioclase is labradorite. Here fall four specimens from the 

 Elkhorn district, Montana, on the border of the Butte batholith, 

 described by Barrell.^ The rock, however, is near the border 



' line between Orders 2 and 3. The plagioclase is described as 



' Henry S. Washington, "Italian Petrological Sketches, II: The Viterbo Region," 

 Jour. GeoL, IV (1896), 838. 



'Ibid., V (1897), 351; "The Roman Comagmatic Region," Carnegie Publication 

 No. sy (Washington, 1906), p. 65. 



3 Joseph Barrell, "Microscopical Petrography of the Elkhorn Mining District, 

 Jefferson County, Montana," U.S. Geol. Surv., Ann. Kept., XXII, Part II 

 (1901), p. 538. 



