PHYSIOGRAPHY. 253 



Heavy Spar. 



in a granular composition. The composition is sometimes 

 granular, and even impalpable. Without coherence of the 

 particles, friable. 



1. It decrepitates when suddenly heated before the blow-pipe, and fu- 

 ses with difficulty. Several varieties emit a phosphorescent light, if 

 carefully heated, and retain this property for some time after cooling. 

 In the interior flame, it assumes a burning, hepatic taste. 



2. Analysis. 

 By BERTHIER. 



Baryta 66-00 



Sulphuric acid 34-00 



Several varieties contain substances foreign to this mixture, which 

 must be considered as impurities, as silica, oxide of iron, alumina, &c. 

 Crystals of Heavy Spar have been artificially obtained by dissolving sul- 

 pho-cyanuret of barium in sulphuric acid, and allowing this solution to 

 be slowly decomposed by the influence of the atmosphere ; they are in 

 the form of the primary ; having angles of 101 42' and 78 18'. 



3. Many varieties of Heavy Spar, but more particularly the granular 

 and compact ones, occur in beds, accompanying Galena and Blende ; 

 others are found in iron ores. It is frequently met with in veins, in rocks 

 of various ages, either with the above mentioned, or with cupriferous, 

 minerals; also with manganese ores, Grey Antimony, and Realgar. 



4. Large and beautiful crystals have been found in the mines of Cum- 

 berland, Durham and Westmoreland, in England ; also at Felsobanya 

 and Cremnitz in Hungary, at Freiberg, at Marienberg and other places 

 in Saxony, at Pzribram and Mies in Bohemia, at Roya and Roure in 

 Auvergne. A radiated variety, in imbedded globules, is found at Monte 

 Paterno, near Bologna. The Calcareous Heavy-Spar of BREITHAUPT, 

 is a variety of the present species, found near Freiberg. It contains a 

 little sulphate of lime, in consequence of which its sp. gr. is only 4-2. 



The deposits of this species are too numerous in the United States to 

 be enumerated; only a few of the more important can be mentioned. 

 The curved lamellar varieties are abundant at the Southampton lead 

 mines in Massachusetts, and in several similar places in the vicinity. In 

 Connecticut, similar varieties are found in connection with the trap and 

 sandstone at Berlin, Farmington, and Southington. But the most inter- 

 esting locality is at Cheshire, where it occurs in distinct crystals, as well 



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