14 



ROYAL SOCIETY OF CANADA 

 Minerals which occur in the Syenites. 



The following minerals have been found in the nepheline syenite or 

 its associated alkali syenites. 



Nepheline 



Sodalite 



Cancrinite 



Feldspar 



Scapolite 



Biotite 



Hornblende 



Muscovite 



Corundum 

 Calcite 

 Garnet 

 Zircon 

 Sphene 

 Tounnaline 

 Spinel 

 ■ Chrysoberyl 



Eucolite 



]\Iolybdenite 



Apatite 



Magnetite 



Pyrite 



Pyrrhotite 



Chalcopyrite 



Graphite 



Nepheline. — As a rule the mineral is quite fresh and glassy, break- 

 ing with a sub-conchoid al or uneven fracture. Tlie freshly broken 

 fragments are often distinguishable with difficulty from the plagioclase. 

 It varies from almost colourless to white or very pale grey. Often it 

 possesses a beautiful pale salmon pink colour, which, on inspection is seen 

 to accompany an incipient decomposition of the mineral. A progressive 

 increase in this alteration is characterized by a gradual deepening of the 

 tint until a bright brick red colour is assumed, representing the extreme 

 stages in the decomposition and hydration of this mineral. The resul- 

 tant products in the primary stage are chiefly minute scales of mus- 

 covite, with very brilliant double refi-action, the process extending from 

 certain cracks, and from the margin of the individual or forming 

 " halos " around certain inclusions. Some of the individuals are more 

 or less turbid and opaque as a result of decomposition. In the more 

 highly coloured phases of the mineral an aggregate resembling gieseckite 

 in composition and appearance is produced, giving rise to very brilliant 

 aggregate polarization. 



It is usually comparatively free from inclusions, although sometimes 

 hornblende, biotite, calcite and even feldspars occur enclosed. The 

 hardness of the nepheline occurring at York river according to Dr. 

 Harrington' is nearly 6. The specific gravity at 17°C.=2.62o as deter- 

 mined with the bottle and ?.r>18 by suspension Avith a hair. Before the 

 blowpipe it fused quietly at about 3.5 to a colourless slightly vesicular 

 glass. An analysis of this nopheline by T)r. Harrington gave the follow- 

 ing results (under T). For (•oini)avisoii an analysis of the yellow variety 

 of nepheline of Coimbatore. Madras, India, is given under 11.- 



'Amer. Jour. Sc. Vol. XLVIII. (1894). p. IT. 



'Mem. Geol. Surv. Ind., Vol. XXX. Part TTT. 1901. p. 



181 



