New Occurrence of Rutile and Sapphirine. 271 



age being somewhat smaller (0*4 or 0*7 mm ). Quantitative 

 estimates of the amount present indicate something like 3-5 

 per cent for the general run of the rutile-bearing rock. 



No trace of crystallographic outline has been noted on the 

 sapphirine and there is only a faint suggestion of two inter- 

 secting cleavages. The fracture is marked, being developed 

 in the form of prominent irregular cracks and is highly con- 

 choidal. The pleochroism is strong, a, pale, smoky brown to 

 almost colorless, b=c, deep sapphire-blue, sometimes with a 

 shade of green. The single refraction is strong, a, having been 

 determined by the immersion method as approximately 1*729 

 for sodium light. The double-refraction is very low, not ex- 

 ceeding 0*005. The interference tints in many sections show 

 deep berlin blues. The optical character is clearly negative, 

 the axial angle rather large, and the dispersion is marked r<v. 

 It is to be noted that the index of refraction is higher than 

 that of the sapphirine from the original locality in Greenland 

 in specimens studied by the writer. 



The sapphirine from India* corresponds to that of the 

 present locality very closely in color, and the index for a has 

 been determined by the writer as about 1*726. 



The sapphirine from St. Urbain shows nearly always a more 

 or less extensive alteration not observed in the case of the 

 Indian and Greenland varieties. This begins as a finely 

 fibrous or foliated development along the curved fracture lines 

 and margins. Further alteration develops a fine aggregate 

 of more distinctly foliated material which suggests talc in 

 appearance. These products become mingled with chlorite, 

 biotite and ferruginous material, resulting from the alteration 

 of the associated minerals, which renders it difficult to deter- 

 mine the exact character of the alteration. Nevertheless, the 

 appearance of the alteration is quite characteristic and as noted 

 above, permit it to be easily seen that the sapphirine was 

 originally more abundant than at present. 



The alteration of the sapphirine, as well as its intimate asso- 

 ciation with the other minerals, made it difficult to obtain 

 suitable material for a chemical analysis. By means of an 

 electro-magnet and heavy solutions, some 3 grins, sapphirine 

 contaminated with the other minerals and alteration products 

 were separated from a sample of rutile concentrates, generously 

 placed at the writer's disposal by Mr. E. R. Berry of the 

 General Electric Company of Lynn. In barium-mercuric iodide 

 solution, grains of seemingly pure sapphirine sank just after 



* Penological Study of Some Rocks from the Hill Tracts, Vizagapatam 

 District, Madras Presidency. Walker and Connor, Records Geological Sur- 

 vey of India, vol. xxxvi, Part 1, 1907. The writer is indebted to Professors 

 Walker of Toronto and Palache of Cambridge, Mass., for specimens of the 

 Indian and Greenland minerals which were studied in this connection. 



