Q2 



tween oligoclase and andesine. Most of the exposures 

 however, contain a variable quantity of deep pink garnet, 

 magnetite and corundum. Under the microscope the thin 

 sections show the presence of subordinate amounts of 

 muscovite, biotite, scapolite and a deep green spinel. 



7. Scapolite rock. — Some of the quarries show the 

 presence of a pale greenish granular rock made up almost 

 exclusively of scapolite. This mineral has a specific 

 gravity of 2-67, showing that it is of intermediate com- 

 position in the scapolite series. Associated with this 

 scapolite are small bands of magnetite. 



8. Amphibolite occurs intimately associated with the 

 other members of the corundiferous series chiefly as dark 

 greenish bands, analogous to similar inclusions in the granite 

 gneiss batholiths. Some bands are highly micaceous, 

 while others are composed almost altogether of hornblende. 

 In some cases they are apparently highly deformed and 

 altered basic dykes. 



9. Corundum syenite pegmatite is the rock which con- 

 tains the largest and most abundant crystals and masses of 

 corundum at Craigmont and thus is the richest 'ore "which 

 has been quarried or mined. This rock occurs in the form 

 of dykes, which sometimes attain a width of eighteen 

 feet. Sometimes these dykes cut across the banding or 

 foliation of the series, but usually run parallel with these 

 structures. There is often a distinct and perfect gradation 

 between this coarse-grained phase and the normal type of 

 syenite (No. 4), which also contains corundum, although 

 in less abundance and in smaller individuals. The rock 

 is made up almost entirely of a deep, flesh-red to very pale 

 salmon pink feldspar, which in thin section under the 

 microscope is seen to be an irregular intergrowth of ortho- 

 clase and albite, the latter, as indicated by the analysis, 

 being the more abundant. Associated with this micro- 

 perthite as accessory constituents, locally and usually in 

 small amount, are biotite, muscovite, scapolite, calcite, 

 magnetite, hematite (micaceous iron ore), molybdenite, 

 pyrite, pyrrhotite, chalcopyrite, chrysoberyl, spinel and 

 quartz. Although quartz and corundum are commonly 

 supposed to be mutually exclusive, specimens have been 

 found containing these two minerals in small amount. 



This syenite pegmatite is representative of the final 

 stages in the crystallization of this highly aluminous 

 magma. 



