1835.} Improvements in Science. 273 



19. Sternbergite. — Zippa finds this composed of 



Silver . . . 33-2 

 Iron .... 360 

 Sulphur . . . 30-0 



99-2 

 equivalent to 4 F Su. + Ag. Su. 



(Poggendorff, Ann. xxvii.) 



20. Melanochroite. — This mineral is found in the neigh- 

 bourhood of Beresow, in the Uralian Mountains, in lime- 

 stone, where it is accompanied with vauquelinite, phosphate 

 of lead, quartz, and galena ; colour between cochineal and 

 hyacinth ; compact ; crystals, rhomboidal prisms, with two 

 large faces, which gives them a tabular appearance ; edges, 

 translucent ; streak, brick-red ; sp. gr. 5*75. Before the 

 blowpipe fuses easily into a brown mass, which assumes a 

 crystalline structure on cooling. In the reducing flame it is 

 converted into oxide of chromium and metallic lead. It 

 consists of Oxide of lead . . 76*36 



Chromic acid . . 23*64 



100-00 



It is obviously, therefore, a subsesqui-chromate of lead. 

 (Poggendorff, xxviii.) 



21. Chrome iron ore, from Baltimore, was found by Abich 

 to contain, {Poggendorff, 1831.) 



Crystallized. Amorphous. 

 Silica ...... — 00-83 



Alumina 11-85 13-85 



Oxide of chromium . . 60*04 54*91 



Protoxide of iron . . 20*13 18*97 



Magnesia 7*45 9*96 



99*47 98*52 



22 White Arseniate of Iron. — Kersten found a specimen 

 of this mineral from Freiberg, to consist of 



Arseniate of iron . . 70*70 

 Water : 28*50 



(Schweigger SeidcVs Jahrbuch, vi. 182) 99*20 



VOL. I. T 



