RE-EXAMINATION OF AMERICAN MINERALS. 155 



of a butterfly. Some of the single crystals are an inch in length 



and half an inch thick. 



A transparent crystal weighing five grammes gave a specific 



gravity of 6.60, and on analysis furnished 



Carbonic acid 16.38 ") +,-, *, 



Oxide of lead 83.76 f — ^ ° 



100.14 

 It occurs in hematite, coating galena in a manner similar to 

 the anglesite, and associated with it; also in connection with 

 pyromorphite, which often colors the entire body of the crys- 

 tals of cerusite. It is found on galena without the association 

 of any other mineral ; on green and blue carbonate of copper ; 

 on pyromorphite, which often covers the entire surface of the 

 cerusite crystals, imparting to them an opaque yellowish-green 

 color; on oxide of manganese, in snow-white crystals, without 

 any other associate; on hematite in a similar manner. Mammil- 

 lary masses of the hematite sometimes pass through the crystals. 

 Some few specimens have been found consisting of crystals of 

 galena, with a number of very fine hemi trope crystals of ceru- 

 site on the surface. The cerusite is occasionally covered with 

 an exceedingly thin coat of oxide of iron, giving the crystals 

 a dark -red appearance ; and some of them again with a very 

 thin layer of pyromorphite, as delicate as if it had been put 

 on with a brush. 



The cerusite is sometimes colored — black, green, and yellow — 

 in a manner similar to that mentioned under anglesite. 



50. WULFENITE. 



This mineral is found in small crystals of every shade of 

 color from a light-yellow to a bright-red. It has been found 

 in some abundance, forming, from the 

 manner of its occurrence, very beautiful 

 specimens. The crystals present a variety 

 of modified forms, tabular and octahedral, 

 one of which is here figured. 



Other forms are 0, 1. 



i 1 Fi s- L 



V J 3 5 x# 



' 0, Jg, go -co . (Fig. 1.) Specific gravity of a 



dark-yellow variety, 6.95. 



The composition of both the yellow and red varieties was 

 mined. The difference of color is due to the presence of 



