OF CENTRAL CANADA PART II. 



85 



crystals, as well as in continuous bands, in dolomite, chlorite slate, 

 serpentine, and other magnesiaii strata. Much of the ore from these 

 localities, however, contains titanium or chromium. Lastly, in the 

 form of black sand, alone, or mixed with Iserine, the ore occurs very 

 commonly on the shores and islands of Lake Superior, Lake Huron, 

 Erie, and Ontario, and on those of many of our smaller lakes. Also, 

 here and there, on the north shore and gulf of the St. Lawrence ; 

 and mixed with the auriferous gravels of the Chaudiere, St. Francis, 

 Gilbert, and other rivers of the Eastern Townships. 



Note : Magnetite occasionally becomes altered by higher oxida- 

 tion into Hematite, without change of form. The streak is then 

 more or less red, and the magnetism scarcely perceptible. Some 

 small octahedrons (with truncated edges) of this character, the Mar- 

 tite of some authors, were observed by the writer in a gneissoid 

 boulder from Bass Lake, a few miles north of Orillia. 



32. Iserine, or Titaniferous Magnetic Ore : Black, with black 

 streak and sub-metallic lustre. More or less strongly magnetic. In 

 minute octahedrons, sand grains and pebbles. Other characters like 

 those of Magnetic Iron Ore, but the glass obtained by fusion in a 

 reducing flame with phosphor-salt has always a distinct red or red- 

 brown colour. Composition, essentially, magnetic oxide of iron, with 

 part of the iron replaced by titanium. A small amount of magnesia 

 is also generally present. Forms a certain portion of most of the 

 black magnetic sands of our lake, island and river shores, referred 

 to under No. 31.* 



33. Chromic Iron Ore : Black or brownish-black, with, normally, 

 a dark brown streak, and sub-metallic aspect ; but the streak is often 

 greenish or greenish-grey, from the presence of intermixed serpentine 

 or other silicious matter. In general, slightly magnetic : if strongly 

 magnetic, the substance is mixed with magnetic iron ore, and the 

 streak is more or less black. Regular in crystallization, but occur- 

 ring commonly in irregular masses, mostly of granular structure. 

 H=5.5 ; sp. gr. 4.34.6. BB, like magnetite, infusible or but 

 slightly rounded on the thin edges. With borax and phosphor-salt, 

 yields a more or less pure green glass, the green colour becoming 

 clearer and more distinct as the glass cools. Composition, theoreti- 

 cally, oxide of iron and sesqui-oxide of chromium, but the latter is 



* For the detection of Titanium in iron ores, generally, the reader is referred to the author's 

 Blowpipe Practice, p. 51. 



