306 ARSENIC. 



passing into steel-grey. It occurs massive or disseminated, also 

 in prismatic distinct concretions, and crystalized in oblique four- 

 sided prisms, variously modified by bevelments and truncations. 

 Externally it is shining or splendent ; internally, shining or glis- 

 tening, with a metallic lustre. The fracture is uneven. The spe- 

 cific gravity is 6*60. It gives fire with steel ; when rubbed it emits 

 an arsenical odour. Before the blow-pipe it gives out white arse- 

 nical vapours, leaving the oxide of iron, which is sometimes mag- 

 netic. According to Dr. Thompson, it contains, arsenic 48" I, 

 iron 36*5, sulphur 15*4. Arsenical pyrites is very abundant in 

 the copper and tin-mines in Cornwall ; and it is from this ore 

 that the white oxide of arsenic and artificial orpiment are princi- 

 pally prepared. 



Sp. 3. Sulphuret of Arsenic. — Of this mineral there are 

 two varieties, the red sulphuret of arsenic or realgar* and the 

 yellow sulphuret of arsenic, or yellow orpiment. 



Bed Orpiment or Ruby Sulphur. Pl. XLITI. fig. 3.— Rothes 

 Rauschgelb, Werner. — The colour is aurora-red, passing into scarlet 

 or orange-red. It occurs massive, disseminated in flakes or mem- 

 branes, and crystalized in oblique four-sided prisms, variously modi- 

 fied. It is soft, yielding to the nail ; the fracture is uneven or 

 conchoidal, and the lustre is resinous, inclining to adamantine. 

 It is translucent or semi-transparent. The specific gravity is 3 - 30. 

 Its constituent parts are, arsenic 69, sulphur 31 = 100. Klaproth. 

 It is found in different mining districts in Germany; also in the 

 fissures of lava in volcanic countries. 



Yellow Orpiment. Pl. XLIII. fig. 4. — Gelbes Rauschgelb, 

 Werner. — Its colour is lemon-yellow, with a brilliant lustre, inter- 

 mediate between adamantine and semi-metallic. It occurs massive, 

 disseminated, and in various external forms, and also crystalized. 

 Its structure is laminar ; it is sectile, flexible, but not elastic. It 

 contains arsenic 62, sulphur 38=100. Klaproth. It occurs in 

 veins in primitive and secondary rocks in various parts of the 

 world. The orpiment of commerce is brought from the Levant. 



Sp. 4. Oxide of Arsenic is said to occur in the Hartz, and 

 in some other places on the Continent, crystalized in quadrangular 

 prisms, also capillary, earthy, and stalactitic. It is of a snow-white 



