652 GEORGE W. BAIN 



and diopside, and the remainder calcite. Minor amounts of 

 phlogopite, garnet, chondrodite, scapolite, and sulphides are also 

 found locally, but their occurrence is always such as to suggest 

 introduction by magmatic emanations from the granite. An 

 inclusion of blue limestone in an aegerite granite dyke of early 

 Laurentian age gave the following analysis : , 



Per Cent 



Diopside and Wollastonite 16.4 



Soluble Iron and Alumina 2.2 



Calcite 81.0 



Dolomite 1. 1 



100. 70 



(The carbonates are given as dolomite and calcite rather than as 

 dolomite or as calcite and magnesite, because when the poHshed 

 surface of a specimen was treated with Lemberg's solution, it was 

 found that the rock consisted of two definite carbonates, the one 

 being calcite, and the other, in an amount demanded by the dolomite 

 ratio, determined by a chemical analysis.) 



Since this fragment of limestone was sealed off from all outside 

 sources of material before the contact effects of the granite became 

 pronounced, it is believed to represent very closely the composition 

 of the original limestone; slight additions of silica from the dyke 

 may have been received. , On the other hand, since the dyke itself 

 is somewhat pegmatitic, the limestone may have undergone mild 

 contact-metamorphism before being effectually sealed away. 



Away from the dyke the limestone has come under the influence 

 of magmatic waters which have produced considerable silication. 

 A typical analysis of the silicated limestone is as follows: 



Proximate Ultimate 



Per Cent Per Cent 



Wollastonite and diopside 30.00 SiOa 16.05 



Soluble iron and alumina 0.25 AI2O3 o. 14 



Calcite 69.62 FeAl 



Dolomite 0.15 FeO / ^'^^ 



CaO 46.65 



MgO 5.25 



Na.O 



K.0 



CO^ 30.80 

 100.43 



