C. H. Warren — Miiieralogical Notes. 343 



The author wishes here to thank Messrs. Horton and Knowl- 

 ton for generously furnishing him with the material for study. 



III. Cerussite cuid Phosgenite from Colorado. 



In making blowpipe tests on some specimens of cerussite it 

 was noticed that when the finely-powdered mineral was heated 

 on a platinum wire in the Bunsen flame, after the color due to 

 the lead had disappeared, a persistent crimson coloration was 

 imparted to the flame, indicating the presence of strontium. 



The cerussite was purchased from Messrs, George L. English 

 & Co. of IS'ew York, and through their courtesy it was learned 

 that it came from the Terrible mine, Isle, Custer Co., Colorado. 



It is crystalline and massive in character, of a prevailing 

 grayish white color, which changes in places to a light amber 

 tint. The surface is discolored with a yellowish brown earthy 

 coating. 



A chemical analysis^ made on carefully selected fragments, 

 having a speciflc gravity of 6*4:09, yielded the following results: 



•387 

 •387 



99-76 



Careful tests were made for barium and calcium with nega- 

 tive results. The ratio is very sharp, PbO + SrO : CO^ = 1:1, 

 and indicates the formula (Pb, Srj CO3 for the mineral. Cal- 

 culated to one hundred per cent, the composition becomes 

 PbCO = 95-52 per cent; SrCOg = 4-4:8 per cent. No stron- 

 tium could be detected in the phosgenite. 



It is, perhaps, not surprising to tind such a notable amount 

 of strontium carbonate isomorphous with the lead carbonate, 

 but, so far as the author has been able to ascertain, it is the 

 first recorded instance of such a carbonate, and adds another 

 undoubted case of isomorphism to those already known among 

 the orthorhombic carbonates. 



By plotting the specific volumes (the specific gravity of lead 

 and strontium carbonates being taken as 6-517 and 3-697 respec- 

 tively) of lead and strontium carbonates as ordinates and the 

 percentages of strontium carbonate as abscissas, a specific grav- 



* The analysis was made by the author while he was connected with the 

 Mineralogical Laboratory of Sheffield Scientific School, during the spring of 

 1900. 









Eatio, 



C0,= 



17-02-^ 



r 44 = 



-387 



PbO = 



79-o9-i 



-223 =2 



-357 



SrO = 



3-15-1 



rl03-3 = 



-030 



Alks. trace. 







FeO tr 



ace. 







