MINERALOGY OF CHALANCHES, 133 



fiickd, in which silver has frequently formed more than one 

 sixth of the mass. 



Arsenical nickel occurs very pure in -nodules, though Arsenical 

 rarely. It is more frequently mixed with cobalt, iron, and 

 silver. Frequently it contains silver enough to be worth 

 working as an ore. This is a combination peculiar to Cha- 

 lanches. Tt is in irregular nodules, of different sizes, capa- 

 ble of being cut and polished. 



Oxide of nickel occurs frequently in fine specimens com- Oxide of 

 monly covering arsenical nickel. It is white, or of a green mckel * 

 more or less deep, and always pulverulent. 



Magnetic oxidulated iron is frequent in the hornblende Magnetic ox- 

 rocks. It is in crystals of an indeterminate form, of a deep ' e ° iron * 

 black colour, and with somewhat of a metallic lustre. 



Oligist iron is very abundant in some veins, is frequently Specular iron 

 found in the strata of gneiss, and is common in those of ore * 

 quartz, and carbonate of lime. 



Sulphuret of iron is not abundant, but sometimes occurs Pyrites, 

 in the veins, and in the rocks. Occasionally it is without 

 its yellow colour and metallic lustre, having acquired a dull 

 and earthy aspect from decomposition. 



Oxided. iron is the most common gangue of the silver ore. Oxide of iron. 

 {Sometimes the silver can be discerned in it by the naked 

 eye; but it is more commonly concealed by the iron, which 

 is more or less coloured and mixed with foreign matters. 



The sparry iron ore has been mentioned already under Iron spar. 

 the head of carbonate of lime. 



Manganese is very abundant in the veins, but hitherto it Manganese. 

 has been found only in the state of oxide. It accompanies 

 the richest silver ores. 



Oxide of zinc occurs, though rarely. Sulphuretted zinc z'ma. 

 is rather more common. Neither of them is crystallized. 



Arsenical cobalt is scarce, never forms veins alone, and Arsenical co- 

 commoHly is destitute of silver. l ' 



Gray cobalt is rather more common, but seldom pure. Gray cobalt. 

 It is frequently mixed with arsenical nickel, and sometimes 

 with silver. 



Black oxided cobalt is very abundant, sometimes pure, Black oxided 

 but commonly mixed with oxides of iron and manganese, cobalt, 

 sulphuret of mercury, and often silver. 



Arseniated 



