' ROGERS, GEOLOGY OF THE CORTLAXDT SERIES 35 



Tiowever, is indicated by its areal distribution; and, as remarked above, 

 it seems to be at once tbe most common and the most resistant member 

 of the norite family. It is itself a transition phase from biotite norite 

 to augite norite ; it rarely shows relations with other types. 



Quartz Norite 



The remarkable rock, quartz norite, was found in only one area, at the 

 extreme southern point of the series, where it lies between biotite norite 

 and mica schist. This and similar quartz-bearing rocks were also found 

 in the emery mines, but the peculiar conditions which undoubtedly gov- 

 erned the formation of these deposits tend to discredit the occurrence of 

 such rocks over larger areas, and they will therefore be described in the 

 economic section of this article. The patch in question might perhaps 

 be relegated to the same category, as purely a contact development; but 

 since there is no emery present, and since quartz is known to occur in 

 other gabbros as a result of purely igneous 29 action, it is thought best to 

 notice it here. 



The rock in hand specimen is of a basic, micaceous, brownish gray ap- 

 pearance. In the slide, the feldspar is seen to make up about one-third 

 •of the rock, and about one fifth of it is unstriated. It is distinctly gray 

 from inclusions and shows somewhat wavy extinction. In the case of 

 the plagioclase, the twinning is often irregular. The quartz is present in 

 •considerable quantity and appears to be undoubtedly original. It is in 

 fairly large grains, which fill the interstices between the other minerals. 

 It is often cracked, and these cracks are only occasionally rehealed. The 

 hypersthene constitutes about one-quarter of the rock. Its color is deep 

 and its pleochroism strong, and it carries numerous inclusions. It is 

 altering to bastite and apparently to hornblende also, in places. Only a 

 few grains of the typical green augite were noticed. The biotite makes 

 up about one-quarter of the rock; it is typical and somewhat altered, so 

 that it has a greenish tint. The hornblende is largely secondary, but one 

 or two (deep green) pieces may be original. Apatite is abundant, and 

 there is considerable ilmenite and pyrite. Chlorite, bastite, hornblende 

 and kaolin are the alteration products. 



The rock has undergone a small amount of shearing, but the alteration 

 is probably largely superficial. It appears to the writer that this rock is 



29 J. P. Iddings, "Origin of Primary Quartz in Basalt," Amer. Jour. Sci.. (3), XXXVI, 

 208. 1888. This paper deals with a somewhat different rock, but quartz norite itself 

 has been described by Teller and von John, "Beitrage zur Kenntniss der dioritischen 

 Gesteine von Klausen in Siidtirol," Jahrb. der k. k. geol. Reichsanstalt, XXXII, 5S9-G84. 

 1882. 



