786 ABSTRACTS OF PAPERS 



Mountain and the tinguaite with the tinguaite from Brones Mountain, These 

 are the two most easterly hills of the Monteregian series. 



BLEACHING OF GRANITE AT LIMESTONE CONTACTS 

 BY H. P. GUSHING 



{Abstract) 



In the Thousand Island region, on the New York side, there is a large repre- 

 sentation of Grenville limestones, quartzites, and schists which are cut through 

 and cut out by bathyliths of Laurentian granite gneiss. The ordinary color of 

 the granite gneiss and of its dikes is red, but at limestone contacts the color 

 changes to white, and all the granite dikes in the limestone are white. Both 

 colors are unquestionably primary ; in other words, the granite solidified as 

 red granite except when affected by the limestone, and the field relations show 

 plainly that it was some influence exerted on the granite by the limestone at 

 /he time of solidification that caused the color change. 



The red color of the feldspar of the ordinary granite seems due to the pres- 

 ence of ferric oxide in free condition. It remained uncombined at the tem- 

 perature of solidification. In the presence of calcium carbonate, however, it 

 entered into combination, and into comparatively colorless combination. Ex- 

 periments seem to show that it is the lime rather than the carbon dioxide 

 which was efiRcacious in causing the change, but certainty has not been attained 

 in the matter ; nor is it at all certain what compound was formed. 



This color change seems to us to suggest in some cases a comparatively 

 simple method of determining approximately the temperature of solidification 

 of granites. It also suggests a reason for the scarcity of lime-soda feldspars 

 of red color. 



BARITE DEPOSITS OF FIVE ISLANDS, NOVA SCOTIA"^ 

 BY CHARLES H. WAEREN 



(Abstract) 



Barite deposits occur about 2 miles north of Five Islands, Nova Scotia, a 

 village located 12 miles east of Parsboro, on the north shore of Minas Basin. 

 The principal outcrops are on the steep banks of the bars and East River, and 

 at isolated points between for a distance of some 2 miles. The barite is 

 coarsely crystalline and remarkably pure. It occurs in the form of large, 

 irregular, veinlike masses, usually with steep dip, associated stringers, and 

 smaller isolated masses in an ancient fault breccia;- also as a filling for fis- 

 sures, sometimes several feet wide in the massive ledge rock. The fault 

 breccia is part of an extended zone of faulting, frequently marked by breccia- 

 tion and fissuring, which lies in a narrow east-west band of much folded 

 Dovonic slates and quartzites on the southern side of the Cobequid Hills. 

 The fault zone follows rather closely the contact with intrusive syenites which 

 form the core of the hills. Near the eastern end of the fault zone, north of 

 Londonderry, barite also occurs associated with much ankerite and iron ore, 



15 Read by title by request of author, to expedite the programme. 



