154 RE-EXAMINATION OP AMERICAN MINERALS. 



crystals, whose form is not altered. There are crystals of a 

 delicate green color arising from carbonate of copper, and 

 others of a yellow color due to oxide of iron. 



The transparent and colorless variety is remarkably pure. 

 Its sp. grav. is 6.35. On analysis it afforded 



1 2 



Sulphuric acid 26.78 26.61 



Oxide of lead 73.31 73.22 



Silica t .20 ......... 



100.29 99.83 



according very precisely with the formula Ph s. 



I would call attention to the method of analyzing this 

 sulphate, as described in another paper, for it was analyzed 

 in the moist way by dissolving it first in citrate of ammonia. 



The anglesite of this mine is found variously associated. It 

 is common to find it in geodic cavities in galena, the cavities 

 being lined with hematite varying in thickness from -^ to -^- an 

 inch or more, and often this hematite contains anglesite inti- 

 mately mixed in the mass. It may occur in crystals occupying 

 a portion of the geode, or it may fill its entire capacity, assum- 

 ing the form of the cavity. It is also found compacted in the 

 galena without the appearance of any cavity or the presence 

 of any other mineral; acicular crystals occur diffused through 

 the galena. Observed also on copper pyrites, with a thin layer 

 of hematite intervening between the crystal and the pyrites — 

 on crystals of zinc-blende in quartz — on quartz associated with 

 pyromorphite — on galena with crystals Of sulphur — on calc- 

 spar without any associate. One very interesting specimen 

 consists of a flattened crystal an inch square, having a delicate 

 crystal of calc-spar over an inch and a half in length perfo- 

 rating the center and around which the sulphate appears to 

 have formed. It is also found on fluor-spar without associate. 



Some of the most beautiful specimens are where large crys- 

 tals of anglesite are covered with crystals of carbonate of lead, 

 these latter frequently penetrating the anglesite. 



49. Cerijsite. 



The crystals of this mineral, though not as large as those 

 of anglesite, are yet exceedingly beautiful, both in size as well 

 as transparency. The twin crystals are often two inches broad, 

 transparent, and presenting the appearance of the spread wing 



