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THE ROYAL SOCIETY OF CANADA 



rests as loosely compacted, and more or less freely developed, capillary 

 crystals up to }4 of an inch in length. 



The best specimens were obtained from a fissure about 3 inches in 

 width, which was completely filled with thaumasite in the form of 

 mealy masses, somewhat loose in texture. These also are built up 

 of capillary crystals, aggregated together with a tendency towards a 

 feathery arrangement, and the specimens show a somewhat fibrous 

 structure when broken. The material for analysis was selected from 

 these specimens, and it was found to be remarkably pure, only 0-3 

 per cent, remaining undissolved in cold dilute hydrochloric acid. The 

 analysis yielded the following result: — 



The ratios agree fairly closely with the established formula, 

 3CaO. SiO.2. SO3. COo. I5H2O. Both the silica and the carbon dioxide 

 are a little low. Three determinations of the carbon dioxide gave 

 6-66, 6-71, and 6-71 per cent. The water was determined by the 

 Penfield direct method. 



The specific gravity was determined as 1 -877 by the pycnometer 

 method, and 1-879 using Thoulet solution. This agrees with the 

 value usually assigned to thaumasite, but is higher than that found by 

 Schaller for the Utah material (Sp. G. =1-84). The remaining 

 physical properties, and the optical characters, so far as they could be 

 determined, are as usual for thaumasite, and call for no comment. 



Thaumasite has not previously been recorded from Canada; 

 indeed, this peculiarly constituted mineral appears to be of somewhat 

 rare occurrence, having been noted only at one or two localities in 

 Sweden and the United States. It was first described in 1878 by Baron 

 von Nordenskiold,^ from the copper mines of Areskuta, Jemtland, 

 Sweden, and it has since been found at two other neighbouring locali- 

 ties in that country. In the United States, the occurrence of the 

 mineral at Berger's Quarry, West Paterson, New Jersey, was described 



iCompt. Rend., vol. 87, 1878, p. 313. 



