[HOWARD] SOME OUTLIERS OF THE MONTEREGIAN HILLS 



87 



the average size being less than 0.1 mm. by 0.01 mm. The biotite is 

 deep brown in colour, and is strongly pleochroic in dark brown shades. 



These basic minerals are more abundant near the contact than 

 at a short distance away, although they are nowhere abundant in 

 this phase. In fact, only a few millimetres from the contact they are 

 confined to a few scattered grains. 



The groundmass also varies in composition as it approaches the 

 contact. Less than a centimetre away it is composed very largely 

 of the isotropic, with the exception of a few irregular grains of calcite 

 and laths of the feebly biréfringent zeolite, heulandite. Frequently 

 these laths have an isotropic centre symmetrical with the lath, and 

 locally there are irregular areas a millimetre or so in diameter where 

 heulandite and calcite occur practically to the exclusion of the base. 



Labradorite occurs in very small am^ount, but the quantity in- 

 creases towards the contact with the normal type where they form the 

 greater part of the groundmass. 



The groundmass of this later intrusion is thus very similar to that 

 of the areas surrounded by aegirite-augite in the earlier rock and this 

 probably represents an injection of the magma from below after the 

 solidification of the greater part of the basic constituents of that 

 magma. 



Chemical Analysis of Fourchite, Ste. Dorothée 

 Analysis by W. V. Howard 



SiO, 44.43 



Al,02 14.02 



FesOg 



FeO.. 



MgO. 



CaO.. 



NasO. 



K2O . . 



H2O.. 



TiOs . , 



MnO. 



P2O5 . . 



CO2.. 



4.86 

 6.09 

 4.08 

 11.53 

 4.14 

 1.73 

 1.96 

 3.03 

 0.04 

 0.83 

 2.77 



99.53 



Or 10.01 



Ab 29.87 



An 14.46 



Ne 2.84 



Di 15.36 



01. 

 Mt 

 II.. 

 Ap. 



3.36 

 7.19 

 5.78 

 2.02 



Spec. grav. 3.11 



CO2 equivalent to CaCOs 6.30% 



(II) III. 5. (2)3. 4("3. 2. 2". 3; 



Classification 

 Salfemane 

 perfelic 



alkalicalcic (camptonase) 

 dosodic (comptonose) 



