F. D. Adams — Nepheline Syenite in Ontario. 13 



sections shows a very strong pleochroism, from pale yellow to 

 a very deep brown. In basal sections it is seen to be distinctly 

 biaxial but the axial angle is very small. It is usually quite 

 subordinate in amount. 



Hornblende. — Like the mica this constituent is usually 

 present in comparatively small amount. It is always green in 

 color and frequently presents more or less perfect crystalline 

 outlines, with faces of the prism, clinopinacoid and domes. 

 The prismatic cleavages at angles of about 124° are well seen. 

 Two varieties have been observed. One of these from- near 

 the York River has a large axial angle and shows a pleochroism 

 in tints varying irom deep green to pale yellow, the absorption 

 being c^>b>a. Before the blow- pipe it fuses with intumes- 

 cence to a black glass, giving at the same time a strong soda 

 flame. This variety probably contains a considerable quantity 

 of soda, but approaches common hornblende in composition. 

 The second variety, which occurs in an exposure about two 

 miles east of the village of Bancroft, has a much stronger 

 pleochroism in tints varying from very deep bluish-green to a 

 yellowish-green and has a small axial angle and a high extinc- 

 tion. Hornblende is not common in nepheline syenite and 

 the only occurrence in which I have seen this particular vari- 

 ety is that which forms part of the Montreal mountain. Here 

 what appears to be exactly the same hornblende occurs inter- 

 grown with augite. It has a very high specific gravity and is 

 probably rich in soda and allied to arfvedsonite. A chemical 

 examination of this hornblende will be made by Dr. Har- 

 rington. 



Scapolite. — This mineral is present in about one-half of the 

 slides and occurs in large clear colorless grains. It has the 

 appearance of an original constituent. Basal sections present 

 the usual double set of cleavages crossing at right angles while 

 sections in the prismatic zone show a single set of cleavages 

 with extinction parallel to them. In convergent light it is 

 seen to be uniaxial and negative. The double refraction is 

 much stronger than in the case of nepheline, the interference 

 colors being tints of red, blue and yellow. The two minerals 

 are therefore easily distinguished. As the occurrence of 

 scapolite in such a rock is very unusual and in order to 

 make sure that the mineral was not cancrinite, a thin section 

 was treated with concentrated hydrochloric acid at first in the 

 cold and subsequently with hot acid. The nepheline was 

 strongly attacked and when the slide was subsequently treated 

 with fuchsine became deeply colored. The scapolite however 

 remained quite unaffected, even after the acid had been actu- 

 ally boiled upon the section. In another section also in which, 

 under the action of the weather, the nepheline was quite de- 



