18 Macfarlane on the Frimitive Formations 



The serpentines of the Laurentian formation, are described by Mr. 

 Hunt as of a paler colour than those of the raetamorphic series* 

 He failed to detect either nickel or clirome in them,and in his exam- 

 ination of a serpentine said to be from Modum in Norway, (proba- 

 bly that of Snarum, from its being associated with ilmenite), these 

 metals were also absent. This is consequently another point 

 of resemblance between the serpentines of the Laurentian formation 

 and those of the Norwegian gneiss formation, distinguishing both 

 of them from the serpentines of the metamorphic series. The crys- 

 talline limestones of the Laurentian formation appear to be much 

 more frequent, and more regularly interstratified than those of the 

 Noiweo-ian gneiss formation, and this is one of the features in 

 which a difference is remarkable between the two formations. 

 In the Laurentian, as in the Norwegian gneiss formation, 

 the gneiss is the prevailing rock, and interstratified with most of 

 the rocks above mentioned. The strike of the strata of the Lau- 

 rentian formation is most generally N. E. and S. W; or W. N. E- 

 and S. S. AV. and the dip much inclined, though perhaps gene- 

 rally less so than ihose of the Norwegian gneiss formation. 



With regard to the economic minerals of the Laurentian form- 

 ation, the existence of falilbands similar to those of Norway seems 

 to be uncertain. Still we find in the Geological Reports, descrip- 

 tions of red-weathering rocks, which bear no slight resemblance 

 to them, and should they be found to possess the character of 

 fahlbands, a search for economic minerals in connection with 

 them, would most like'y be successful, because the metalli- 

 ferous area is limited and well defined. The colour of the rock 

 would assist in tracing it along its strike, and any veins cros- 

 sing it or occurring in it would be easily recognised. Whether 

 the pyrites of Daillebout occurs in connection with a fahl- 



agdite we have an intimate mixture of pyroxene with hornblende, afiford- 

 inga transition to rocks composed of triclinic feldspars and hornblende ; 

 ia other words to diorite and diabase. Those rocks which consist of 

 such feldspars, with diallage or hypersthene, I arrange under the generic 

 name of dolerite. When the feldspar in these predominates, and is gran- 

 ular or compact, including masses of diallage, the rock has been in- 

 correctly called euphotide. This name was originally given by Haiiy 

 to a mixture of diallage or smaragdite with what he called saussurite, 

 a mineral which by modern lithologists has been strangely confounded 

 with compact feldspar, from which it is distinguished by its much great- 

 er gravity and hardness, and is, as I have elsewhere shown, a compact 

 zoisite or epidote. The true epidotic euphotides however sometimes in- 



