128 MINERALS AND GEOLOGY 



ter. Although rarely yielding more than 25 or 30 per cent, of iron, 

 clay ironstone, as occurring in the Carboniferous strata of Europe 

 and the United States, supplies a large nnniber of furnaces, and. 

 yields metal of good quality. The nodules have usually a strongly- 

 marked slaty structure and, when broken, they almost invariably 

 exhibit the impression of a fern frond, fish skeleton, or other organic 

 body. Small fragments after ignition before the blow-pipe, or in a 

 glass tube held over a common spLit lamp, assume at first a red 

 colour, and then become black and magnetic. 



93 bis. Strontianite : This carbonate is stated by Dr. B. J. Har- 

 rington to occur in the form of white fibrous tufts in cracks in some 

 concretionary limestone masses in the Utica slate of St. Helen's 

 Island, Montreal. It imparts a crimson colour to the blowpipe 



flame. 



(2) GROUP OF HYDROUS CARBONATES. 



[This group is only represented in Canada by the somewhat proble- 

 matical Dawsonite, and by the two cupreous carbonates Malachite 

 and Azurite ; and these latter species do not occur in well character- 

 ized examples, but merely as incrustations on Copper Ores, or in the 

 form of stains and small earthy masses in copper-holding rocks.] 



94. Dawsonite : In white, thin-bladecl aggregations or coatings on 

 compact trachyte, Montreal, H = 3 ; sp. gr. 2.4, contains, according 

 to Dr. Harrington, alumina, soda, lime, carbonic acid, and water. 



95. Malachite or Green Carbonate of Copper : Green, of various 

 shades, with pale-green streak. Monoclinic in crystallization, but 

 crystals exceedingly rare. Mostly in botryoidal masses of concentric 

 lamellar, and fibrous structure ; in earthy coatings on copper ores ; 

 and in the form of streaks and markings in copper-holding rocks. 

 H = 3.5 4.0 (in the solid state) ; sp. gr. 3.7 4.0. BB, tinges 

 the flame green, and becomes rapidly reduced to metallic copper. 

 Soluble in acids with effervescence. Essential composition : carbonic 

 acid 20, oxide of copper 72, water 8. Occurs in small quantities with 

 copper glance, native silver, &c., in a calc-spar vein on Spar Island, 

 Lake Superior, and in small earthy incrustations and markings amongst 

 many of the copper ores and associated veinstones of Lake Superior 

 and Lake Huron, generally. Also under similar conditions in Madoc, 

 Marmora, and various other localities in which copper pyrites occur 

 in larger or smaller quantities ; and especially in the chlorite and 



