86 MINERALS AND GEOLOGY 



always replaced to some extent by alumina, &c., and the iron by a 

 certain amount of magnesia. The sosqui-oxide of chromium thus 

 varies from about 40 to about 60 per cent., in different samples. A 

 variety from Bolton yielded Dr. Skerry Hunt 45.90 per cent., and 

 another from Lake Memphramagog gave 49.75 per cent. 



Occurs abundantly in beds and scattered grains amongst the meta- 

 morphic strata of the Easter Townships and Gaspe, mostly in connec- 

 tion with serpentine or other magnesian rocks, the green colour of 

 these being partly due to the presence cf oxide of chromium. The 

 principal localities comprise : Mount Albert in the Shickshock Range 

 of Gaspe, and the Townships of Bolton, Ham and Melbourne. 

 Chromic Iron Ore is largely used in the preparation of chromate and 

 bi-chromate of potash. 



(3) LlMONITE GROUP OF IRON OXIDES. 



34. Brown Iron Ore or Limonite (including Bog Iron Ore and 

 Yellow Ochre): Brown, brownish-black, or dull-yellow; streak, 

 yellowish-brown or ochre-yellow. Aspect, sub-metallic in some of 

 the dark varieties, silky and earthy in others. Occurs commonly in 

 masses with botryoidal surface and fibrous structure, or in granular 

 or earthy masses. H 1.0 5.5 ; sp. gr. 3.5 4.0. Heated in the 

 bulb tube, it gives off water, and becomes converted into red oxide. 

 BB, turns red, and then blackens and becomes magnetic. A thin 

 scale, in the forceps, may be rounded on the. thin edges ; otherwise 

 infusible. Composition, essentially, hydrated sesquioxide of iron ; 

 but the amount of water varies considerably, and the more earthy 

 varieties always contain a certain percentage of phosphoric acid, with 

 frequently silica, alumina, oxides of manganese, and humic or other 

 organic acids. In the sub-metallic and silky varieties, the average 

 amount of metallic iron is equal to about 58 or 60 per cent. ; in the 

 average bog ores it equals about 45 or sometimes 50 per cent. ; and 

 in the ochres, it varies from about 10 to 40 per cent. The average 

 amount of water is about 15 per cent, or from 10 to 20 per cent. 

 Brown and Bog Iron Ores are often smelted, and the Iron Ochres 

 are valuable as a paint material. 



The varieties of this mineral hitherto found in Canada, comprise 

 the more earthy varieties, Bog Iron Ore and Yellow Ochre. These 

 belong 'to comparatively modern deposits, and, in places, indeed, they 

 are now under process of formation. The iron is taken up by water 

 percolating through ferruginous strata, and is held in solution for a 



