42 J. D. Hawkins — Minium from, Leadville. 



reported from Spain (see Dana's Syst. of Min., p. 408), and that 

 Professor Dunnington, of the University of Virginia, dis- 

 covered a similar clay with an ore of zinc from the Bertha 

 Zinc Mines, Virginia, of which the following analysis was pub- 

 lished in No. 1144 of the Chemical News (1881). 



Si0 2 ___ 37*38 



A1 2 3 ..._ 24-67 



Fe 2 3 6-34 



ZnO _. 12-10 



M<_rO ___ -27 



K 2 -47 



Na„0 -27 



H 2 Oatl00° _ 6-69 



H 3 at red heat_._ 10*35 



98-54 

 Missouri School of Mines, Rolla, Mo., Oct. 15, 1889. 



Art. VI. — On Minium from Leadville; by J. Dawson 



Hawkins. 



In 1885, Mr. A. Chanute, while in Leadville, collected some 

 specimens of minium from the " Rock Mine." The specimens 

 lay untouched in his collection until some weeks ago, when he 

 gave me some of the mineral for examination. 



The mineral was found between two ledges of outcropping 

 rock, one of porphyry and the other of limestone, the ore of 

 the mine being carbonate of lead, with occasional occurrences 

 of galenite. The minium does not occur as a solid mass, but 

 is interspersed with cerussite, and close examination also showed 

 small particles of galenite occurring with the cerussile. The 

 galenite found in the analysis, however, is not this. The 

 sample taken for analysis was a very carefully picked one, a 

 lump of the mineral being broken up, and the red particles of 

 minium alone being taken. This sample was again carefully 

 picked over in order to insure the absence of anything else 

 than the pure mineral. The analysis gave the following re- 

 sults : 



Insoluble. 



Insoluble in HC1 7-51 fSi0 2 .__ 2-00 



Pb calculated as PbO -- 91-39 ] AbOFeO -41 



Fe o Q ._.. -80 ) CaO -28 



V 2 6 -52 ^Pb4-42 PbS _ 5'08 



100-22 7-77 



