26 ROYAL SOCIETY OF CANADA 



Zircon. — This mineral is quite comnionly seen in thin sections under 

 the microscope. The microscopic individuals have a rather short pris- 

 matic- form and are as a rule somewhat rounded. In some of the coarser 

 phases of the rock, noticeably at the York river in Dungannon and at 

 Craigmont in Eaglan. ci'ystals are not uncommon which would measure 

 from a quarter to half an inch in length. On lot 32 of con. 11 of 

 Glamorgan, crystals of zircon over an inch in diameter are found in 

 dykes of nepheline syenite, each of these crystals displaying a double 

 tetragonal pyramid. One short stout crystal at present in the Museum 

 of the Geological Survey measures an inch in length by three-quarters of 

 in inch across. These crystals " show two qmte different habits : one 

 in which by the development of two opposite pairs of the pyramidal 

 faces, together with a pair of the prisms of the second order, the crystal 

 becomes columnar in this direction and mimics a hexagonal prism of 

 the second order terminated by rhombohedral faces. In the second 

 habit the pyramidal faces are strongly developed, while the prism faces 

 are short or lacking altogether.*'^ 



Sphene (Titanite). — This mineral is sometimes present although 

 liy no means abundant, and so far as observed, it occurs in microscopic 

 crystals only. It is often in characteristic wedge-shaped thongh some- 

 what rounded forms, hut also' occurs in irregular grains. It is more 

 abundant in the hornblcndic varieties, where it is often quite an im- 

 portant accessory constituent. 



Tourmaline. — This mineral is seen occasionally and in only small 

 amount. It occurs in characteristic crj^stals, which are black in colour. 



Spinel (Aiitomolite) . — A dark green spinel evidently closely allied 

 if not identical with automolite is occasionally found in the nepheline 

 syenite, although it is more abundant in the red alkali syenite. 



Chrysoheryl. This mineral is occasionally met with in the alkali 

 syenite at Craigmont, associated with the corundum. 



Eucolite. — A mineral with the characters of eucolite occurs rather 

 abundantly in the hornblendic variety of the nepheline syenite at Egan 

 chute on the York river as well as at another locality a little lower down 

 on the same stream. It has a yellow colour and usually displays an im- 

 perfect crystallographic form. It is intimately associated with horn- 

 blende and garnet, frequently enclosed in the former and resembling tlu^ 

 latter closely in appearance. It has, however, when examined m iliiii 

 sections, a distinct, though low double refraction with negative sign, liut 

 a high index of refraction with decided relief, a rough surface and paral- 

 lel extinction. It is further distinguished from the garnet by a decided 



'Amer. Jour, Sc. Vol. XI.VIII., 1894, p. 215. 



