268 Warren — -Ilmenite Rocks near St. Urhain, Quebec ; 



Cutting the ore-body in the ru tile-bearing portion is a. streak 

 of anorthosite rock which itself carries more or less rutile. 

 The rutile makes up from two to three per cent of this rock as 

 nearly as it was possible to estimate it. It is associated with 

 ilmenite and a considerable amount of biotite. These minerals 

 are arranged along distinct lines of schistosity. ~No sapphirine 

 has been noted in this rock. 



The rutile-bearing rock is of a brownish black color and con- 

 sists of a rather finely granular ilmenite thickly sprinkled with 

 grains of an orange-red rutile, a smaller amount of feldspar, 

 biotite, sapphirine, or their decomposition products, and spinel. 

 The sapphirine cannot be distinguished without the aid of a 

 good lens, and then only upon very close inspection, about 

 the feldspar and ilmenite grains in the form of very dark, 

 greenish black grains. The less altered ore is firm, but 

 weathered portions are somewhat friable. All of the material 

 collected shows more or less limonite along cracks and joints. 

 In a limited portion of the rutile-bearing rock fairly numerous 

 plagioclase grains or groups of grains, often larger than the 

 average in size, are present. These feldspars sometimes reach 

 a length of two or three centimeters and one centimeter in 

 width, and are characteristically associated with a strong devel- 

 opment of biotite plates. 



Microscopic thin-sections of the rutile-bearing rock disclose 

 a highly xenomorphic texture for all of the constituent 

 minerals with the one exception of the spinel inclusions in 

 some of the feldspar grains. The ilmenite forms an almost 

 continuous background in which the other minerals lie. Its 

 grains, although irregular in outline, are roughly equidimen- 

 sional and are fairly uniform in size, their average cross-section 

 being about 3 mm . They consist of the same lamellar inter- 

 growths as previously described, but the two sets of lamellae are 

 narrower than in the former case, conforming to the smaller 

 average size of the grains. The rutile is in the form of simple 

 crystal grains or clusters of such, and is of a beautiful orange or 

 golden brown color with a barely perceptible pleochroism. The 

 cleavages are prominently developed. Twinning is rare. In- 

 dividual grains attain a diameter of 3'5 mm . From this size they 

 run down to mere specks, the average being in the neighbor- 

 hood of 06 mm . It is distributed quite uniformly through the 

 ilmenite and occurs also with the other minerals, being some- 

 times enclosed in their grains. The spinel is rather sparingly 

 present and forms grains comparable in size to those of the 

 rutile. In the feldspar-rich portions of the rutile-bearing rock, 

 it also occurs included in the feldspars in the form of exceed- 

 ingly minute crystals. These inclusions deserve a brief 

 description. Many of the feldspars are crowded with them. 



