OF CENTRAL CANADA PART II. 131 



and granular gypsum in the Hudson River strata of Cape Rich on 

 Georgian Bay ; and small crystals and crystalline masses are occasion- 

 ally found in cavities of the dolomitic limestones of the Calciferous 

 and Niagara groups, as near Brockville, and in the vicinity of Niagara 

 Falls. Heavy Spar is employed in the manufacture of paints, and is 

 too frequently used in this connection as a fraudulent substitute for 

 white lead. It is also the chief source of the baryta salts of the 

 laboratory. 



98. C destine: White, blue, grey, pale-red, &c. Rhombic in 

 crystallization, the crystals frequently bearing a close resemblance 

 to those of heavy spar. Occurring also in lamellar and crystalline 

 masses, with cleavage angles of about 104, 76, and90, yielding a 

 right rhombic prizm ; and in masses of fibrous or granular struc- 

 ture. H 3.0 - 3.5 ; sp. gr. 3.95 3.97. BB, imparts a crimson 

 colour to the point and border of the flame, and melts into a white 

 alkaline enamel. Dissolves entirely, by fusion, in carb. soda. Not 

 attacked by acids. Normal composition : sulphuric acid 43.6, stron- 

 tia 56.4. This mineral occurs chiefly in sedimentary rock-forma- 

 tions : very rarely in mineral veins or in crystalline rocks. In 

 Central Canada, it is found somewhat abundantly in the interior of 

 small cavities in the Black River or Trenton limestone of Kingston ; 

 and also, with crystals of dolomite, gypsum, fluor spar, blende, and 

 other minerals, in cavities in the Niagara limestone, as in the vicinity 

 of the Falls ; around Owen Sound ; on Drummond Island ; and on 

 the Grand Manitoulin, Lake Huron. A red variety has been 

 recently found by Mr. Roche in freestone of the Medina formation at 

 the forks of the Credit. Celestine is the principal source of strontia 

 salts, used in pyrotechny to impart a red colour to rockets and signal 

 lights, and for laboratory purposes. 



99. Gypsum (Hydrous Sulphate of Lime, Selenite, &c,) : White 

 grey, yellowish, pale-red, fec. Monoclinic in crystallization, the crys- 

 tals very commonly as in Fig. 79 a, or in 



arrow-headed twins as in Fig. b, also in lamellar 

 and foliated crystalline masses with strongly 

 pronounced cleavage in one direction, and in 

 fibrous and granular masses, the latter often 

 forming rock deposits. The cleavage planes 

 present a more or less pearly aspect, the other a FlGi 79> 





