108 PHYSIOGRAPHY. 



Before the blowpipe it melts into a vesicular glass, and 

 loses its colour. It effervesces if melted with glass of bo- 

 rax, and forms a transparent globule, which becomes yel- 

 low on cooling. According to L. GMELIN, it consists of 



Silica 35-48. 



Alumina 18-87- 



Lime 12-00. 



Sulphuric Acid 12-39. 



Potash 15-45. 



Oxide of Iron 1-16. 



Water 1-20. 



It occurs at Albano and Frascati near Rome, among the 

 products of Vesuvius. Also in the neighbourhood of the 

 Puy de Dome, on the lake of Laach, in the quarries of 

 Niedermennich, and in several other places near Ander- 

 nach, partly imbedded in pumice. 



HTSINGERITE. 



Hisingrit. BERZELIUS. Afhandl. i Fysik, &c. III. S. 

 304. Hisingerite. PHILL. p. 204. 



Massive. Cleavage distinct in only one direction. 



Fracture earthy. 



Colour black. Streak greenish-grey. 

 Sectile. Soft. Sp. Gr. = 3-045. 



If gently heated before the blowpipe, it becomes magne- 

 tic ; in a stronger heat it melts into a dull opake black 

 globule, and yields a yellowish-green glass with borax. It 

 consists, according to BERZELIUS, of 



Oxide of Iron 51-50. 



Silica 27-50. 



Alumina 5-50. 



Oxide of Manganese 0-77* 



Volatile substance 11*75. 



Magnesia a trace. 



It has been found in the parish of Svarta in Siiderman- 

 land, intermixed with rhombohedral Lame-haloide. 



