MINERALOGY. 467 



lie in dark-colored varieties, sub-transparent, translu- 

 cent, opaque. By burning in a matrass, it wholly sub- 

 limates ; triturated with iron filings, and afterwards 

 melted, forms metallic quicksilver, and is highly valu- 

 able for silvering mirrors, employed also for thermome- 

 ters, barometers, and is indispensable for various pur- 

 poses in medicine and the arts. Principal localities, the 

 mines of Almaden in Spain, Idria in Austria, Peru, 

 Mexico, New Granada, and China. Cinna,bar ore is the 

 great source of the mercury of commerce, from which it 

 is obtained by sublimation. H. = 2.0 to 2.5. G. = 8.6 

 to 8.7. Used also as vermilion, a well known valuable 

 pigment. 



~Yellow Orpiment Ranschgelb Yellow Sulphuret 

 of Arsenic. Crystals massive, foliated, columnar, some- 

 times reniform ; luster resinous or pearly ; color different 

 shades of lemon yellow ; streak, paler yellow, translu- 

 cent, sectile ; thin laminae obtained by cleavage, flexible. 

 Burns on charcoal with a whitish-yellow flame, and 

 emits fumes of sulphur and arsenic, which are its com- 

 ponent parts. Found in veins in the mining regions of 

 the Hartz, Siebengebirgen, Tyrol, also in the volcanic 

 districts, where it is the result of volcanic sublimation. 

 H. = 1.5 to 2.0. G. = 3.4 to 3.5. Is very poison- 



FOUBTH OEDER. 



PURE OR NATIVE ORES. 



METALS MORE OR LESS PURE, OR NATIVE METALS. 



Pure or Native Iron is steel-gray, passing into silver- 

 white, after casting black; luster metallic, magnetic; 



