[ADAMS & BARLOW] ALKALI SYENITES OF EASTERN ONTARIO 



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microscope, is seen to be an irregular intergrowth of orthoclase and al- 

 bdte, the former feldspar being the more abundant. Associated witli 

 this microperthite are corundum, biotite, scapolite, calcite, magnetite, 

 hematite (micaceous iron ore), molybdenite, pyrrhotite, chalcopyrite, 

 chrysoberyl, spinel, and quartz. All these, with the exception of the 

 first mentioned, occur as accessory constituents in certain places and 

 are usually present in small amount. Although quartz and corundum 

 are commonly supposed to be mutually exclusive, specimens have been 

 found in which small quantities of both of these minerals are present. 

 An analysis of a typical specimen of the corundum syenite pegmatite 

 from Craigmont was made by Mr. M. F. Connor, B.Sc, the results ad- 

 justed to a basis of 100 are given under I. For purposes of comparison 

 the analyses of the corundum syenite pegmatite and of the corundum 

 syenite from Nikolskaja Ssopka in the Urals, Kussia, are included under 

 II and III. (Tschermak's Min. und Petr. Mittheil., XVIII, 1898, 

 p. 219). Under I (a) is given the analysis of I, omitting the corundum 

 and recalculating it to a basis of 100. Under II (a) and III (a) are 

 similarly included analyses of II and III, in which the corundum is 

 omitted and the remaining constituents recalculated to a basis of 100. 

 Under IV is an analysis of the separated microperthite from the corun- 

 dum syenite pegmatite of Craigmont, Ont. Under V is an analysis of a 

 similar feldspar from the corundum syenite pegmatite from Sivamalai, 

 Indiia. (Mjem. Geol. Surv., India, Vol. XXX, Part 3' 1901, p. 202). 



