GUIDE TO THE MINERALOGIC COLLECTIONS 51 



Mercury Hg 



Mercury is remarkable as being almost tlie only mineral 

 occurring in the liquid state. It is found in small white metallic 

 globules scattered through its gangue, which is usually its own 

 sulfid, cinnabar. 



It occurs chiefly in clay shales and schists. 



Platinum Pt(Fe) 



Platinum as it occurs in nature is almost invariably alloyed 

 with iron and usually with small quantities of the rarer metals. 

 It is found in small malleable grains or nuggets of a steel-gray 

 to white color scattered through alluvial sand and associated 

 with gold. It is often mined with the gold from these placer 

 deposits. 



A large proportion of the production of platinum is taken 

 from the placer deposits of the Ural mountains. It is also 

 known to occur in Borneo, Brazil and the United States of 

 Colombia. 



Platinum is practically infusible and is consequently used to 



a large extent for chemical apparatus which is required to 



resist a high degree of heat. 



Iron 

 See under meteorites. 



SULFIDS, SELEXIDS, TELLIRIDS, ARSEXIDS, AXTIMOXIDS 



SULFIDS, ETC. OF THE SEMIMETALS 



Realgar AsS 



Realgar is a monosulfid of arsenic. It occurs in translucent, 



orange-red granular masses with a resinous luster, also in 



transparent monoclinic crystals, which are short prismatic in 



habit and are striated vertically. 



Realgar is found in Hungary and in the island of Borneo; it 



also occurs in Utah, California and Wyoming. It is used ;is a 



pigment. 



Orpiment As.,S 3 



Orpiment is the trisulfid of arsenic. It sometimes occurs in 



imperfect orthorhombic crystals but more generally in foliated 



or columnar masses of a brilliant lemon-vellow. When foliated 



