272 



METALS. 



8mithsonite. — Carbonate of Zinc, 



Rhombohedral. R : R = 107° 40'. Cleavage rhomb,' < 

 hedral, perfect. Massive or incrusting ; reniform and sta)« 

 actitic. 



Color impure white, sometimes green or brown ; streak 

 uncolored. Luster vitreous or pearly. Subtransparent to 

 translucent. Brittle. H = 5. Gr = 4*3 — 4-45. 



Composition : oxyd of zinc 64*54, {four-fifths of which is 

 pure zinc,) and carbonic acid 35*46. Often contains some 

 cadmium. Infusible alone before the blowpipe, but carbonic 

 acid and oxyd of zinc are finally vaporized. Effervesces in 

 nitric acid. Negatively electric by friction. 



Dif The effervescence with acids distinguishes this 

 mineral from the following species ; and the hardness, diffi- 

 cult fusibility, and the zinc fumes before the blowpipe, from 

 the carbonate of lead or other carbonates. 



Obs. Occurs commonly with galena or blende, and usu- 

 ally in calcareous rocks. Found in Siberia, Hungary, Sile- 

 sia ; at Bleiberg in Carinthia ; near Aix-la-Chapelle in the 

 Lower Rhine, and largely in Derbyshire and elsewhere in 

 England. In the United States, it is abundant at Vallee's 

 Diggings in Missouri, and at other lead " diggings" in Iowa 

 and Wisconsin ; also in Claiborne county, Tenn. Sparingly 

 also at Hamburg, near the Franklin furnace, N. J. ; at the 

 Perkiomen lead mine, Pa., and at a lead mine in Lancaster 

 county ; at Brookfield, Conn. 



Zinc bloom is an earthy carbonate of zinc, containing 69 per cent, of 

 oxyd of zinc, and 15 of water. From Bleiberg, Carinthia. 



calamine. — Silicate of zinc, 



Trimetric. In modified rhombic prisms, the opposite ex 

 tremities with unlike planes. M : M = 103° 54'. Cleavage 

 perfect parallel to M. Also massive and incrusting, mammil- 

 lated or stalactitic. 



Color whitish or white, sometimes bluish, greenish, oi 

 brownish. Streak uncolored. Transparent to translucent. 

 Luster vitreous or subpearly. Brittle. H=4*5 — 5. Gr = 

 3*35—3*49. Pyro-electric. 



What is the usual appearance of calamine 1 What is its constitution 

 and the effects before the blowpipe ? What effect is produced by fric* 

 tion ? What are distinguishing characteristics 1 How does it occur 

 What is electric calamine 1 



22 



