NO. 1801. MISCELLANEOUS MINERALOGICAL PAPERS— POGUE. 575 



phlogopite from Ontario, Canada, containing a network of colorless 

 crystals, crossing at angles of 60°, which he proved chemically to 

 be pure titanium dioxide. He thought this rutile to be a product 

 of decomposition, because it increased in abundance with the degree 

 of alteration of the mica. 



Rosenbusch "' in 1885 attributed the asterism of the Canadian 

 micas chiefly to the presence of tourmalines of microscopic dimen- 

 sions, though adding that in some instances rutile is present, causing 

 asterism. 



Lacroix ^ the same year made a study of the inclusions in phlogo- 

 pite from Templeton, Canada. These he succeeded in isolating by 

 treatment with hydrochloric acid in a closed vessel heated to 250°, 

 and obtained with them a strong qualitative test for titanium. In 

 1889 " he noted similar inclusions in a phlogopite from Ceylon. 



In 1890 Clarke and Schneider'^ submitted a sample of Burgess 

 phlogopite to W. Lindgren for microscopic examination of its inclu- 

 sions. It was concluded that the needles corresponded well in their 

 optical properties with tourmaline, but no boron could be found in 

 the mica to prove its presence. 



Osann * in 1899 became interested in the inclusions in phlogopite 

 from Ottawa. He found these to occur as laths and variously shaped 

 plates, with parallel extinction and positive elongation, which were 

 unattacked by hydrofluoric acid and would scratch glass. These 

 data being insufficient for identification, he submitted 0.0466 grain 

 for chemical determination to Professor Jannasch, of Heidelberg, who 

 reported ZrOg (?), TiOg (yellow coloration with H2O2), K, Na, traces 

 of Fe, and H2O (?), and thought that the mineral could not be rutile 

 because the HjOj reaction was "much too weak." No definite con- 

 clusion was therefore reached. 



CanavaK in 1901 mentioned the occurrence of sagenetic rutile 

 needles within the biotite of a garnet and graphite gneiss from 

 Lading, Carinthia, but did not give the data upon which he based 

 his determination. 



The writer has examined a number of Canadian phlogopites show- 

 ing asterism, and has found in each instance inclusions identical with 



aH. Rosenbusch. Microscopische Physiographie, 1885, p. 487. 



&A. Lacroix. Sur les inclusions de la phlogopite de Templeton (Canada). Bull. 

 Soc. Min. France, vol. 8, 1885, pp. 99-102. 



cA. Lacroix. Contributions a I'etude des gneiss a pyroxene et des roches a wer- 

 nerite. Bull. Soc. Min. France, vol. 12, 1889, pp. 341, 342. 



<^F. W. Clarke and E. A. Schneider. Experiments upon the constitution of the 

 natural silicates. Pt. 5, The Micas. Amer. Journ. Sci., vol. 40, 1890, pp. 411, 412. 



« A. Osann. Notes on certain Archaean rocks of the Ottawa Valley. Geol.' Surv. 

 Canada, vol. 12, 1899, pt. O, pp. 1-84. 



/R. Canaval. Bemerkungen iiber das Kiesvorkommen von Lading. Jahrb. 

 naturh. Mus. von Karnten, vol. 26, 1901, pp. 1-9. 



