44 
MUSEUM BULLETIN NO. 27. 
Nos. 2, 3, and 4 to crystals from Alatale, and Nos. 5 and 6 to crystals from 
Nordmark. 
No. 
a 
fi 
r 
2V 
2E 
Bx a A c-axis 
1 
1*669 
1*676 
1*698 
59° 
29' 
112° 
30' 
38° 
21' 
2 
1*6707 d 
1 *6776 D 
1*6996 D 
59 
09 
111 
47 
3 
1*6751 
— — 
59 
18 
111 
55 
38 
49 
4 
1*6768\ 
1-6758/ 
• 
59 
15 
38 
41| 
5 
1*6710 
1*6780 
1*7000 
58 
43 
39 
06 1 
6 
— 
1-69359 
58 
52 
38 
031 
All the above are for yellow (sodium) light, with the exception of 2 which gives 
the values for the D line. 
2. Dufet, Bull. Soc. Min., Paris, 1887, 10, 221. 
3. A. Schmidt, Groth's Zeitschr, 21, 11. 
4 and 5, Wulfing, Beitr. Pyroxenfam, Heidelb., 1891, 17. 
6. Flink, Groth's Zeitschr., 11, 485. 
AUGITE. 
Augite and diallage are not found in the area except as rock-forming 
minerals, being essential constituents of the pyroxenite, gabbro, and 
diabase masses. 
AMPHIBOLE. 
The minerals of this group occur only sparingly in the area. The 
typical granite is a hornblende variety, and the hornblende is frequently 
altered in a very peculiar manner, which was first described by F. D. 
Adams. 1 Three stages of alteration were distinguished by Adams, 
as follows: “(1) The hornblende changes to a scaly mass having all the 
appearance of chlorite. This zone is not always present. (2) There is a 
zone of fine needles, generally in tufts, with parallel extinction, and which 
have a brown or yellow colour. This colour, however, does not belong 
to the needles themselves, but is due to the separation of hydrated oxide 
of iron on the decomposition of the hornblende molecule. (3) Running 
out from these tufts are long and exceedingly fine, hair-like needles which 
penetrate the quartz. These are colourless, and probably the same as 
those of the yellow zone, but longer and finer.'* 
Hornblende having a clove-brown colour, in which respect it some- 
what resembles edenite, is found in the gabbro-diorite which forms a 
ridge to the right of a section of the Quebec Central Railway line between 
Black Lake and Thetford about a mile from the former place. In thin 
section the rock is seen to be a quartz-diorite ; the hornblende has a pale 
brown colour, and each crystal individual is surrounded by a zone of 
1 GeoL Surv., Can., Ann. Rept. 1880, 1881, 1882, p. 8A. 
