158- RE-EXAMINATION OF AMERICAN MINERALS. 



is a very abundant ore at the Wheatley Mine, and large quan- 

 tities of it are smelted. Specimens of great beauty are found 

 occurring in botryoidal masses, with columnar structure, in 

 perfect hexagonal prisms, with the summits more or less modi- 

 fied. Crystals are found one half inch in diameter. Some of 

 the crystals are hollow, with only a hexagonal shell. Some- 

 times the crystals are agglomerated in a plumose form. 



A dark-green variety gave a specific gravity of 6.94. No 

 analysis was made of this mineral, as it will be embraced in an 

 examination of the American pyromorphites. 



It is found in decomposed granite, on quartz crystals, occa- 

 sionally covering their entire surface ; in cellular quartz with 

 molybdate of lead ; in large masses of grouped crystals with 

 small crystals of yellow and red molybdate inserted on crystals 

 of sulphate and carbonate of lead, and forming a coating to large 

 surfaces of galena. 



53. Mtmetene. 



The specimens of this mineral that have been found, although 

 few in number, are remarkable for their beauty of crystalliza- 

 tion. Some of the crystals are nearly colorless and perfectly 

 transparent ; others of a lemon -yellow, either pure or tinged 

 with green. The form is that of a perfect hexagonal prism, 

 the edges of the summit most commonly truncated, often to 

 such an extent as to terminate the crystal with a hexagonal 

 pyramid. The crystals are sometimes as small as a hair, and a 

 quarter of an inch or more in length, and again they are so 

 broad and short as to form hexagonal plates half an inch across. 



A specimen of the lemon-yellow variety was examined ; it 

 gave a specific gravity of 7.32, and was found to contain 



Arsenic acid 23.17 



Chlorine 2.39 



Oxide of lead 67.05 



Lead 6.99 



Phosphoric acid 14 



99.74 



corresponding to arsenate of lead 80.21, chloride of lead 9.38= 

 pb 3 As+p>b CI. 



This specimen of mimetene is seen to be almost free from 

 phosphoric acid, containing only about one tenth of a per cent.. 



