L. G. Eakins — Two Sulphantimonites from Colorado. 451 



This mineral comes from the " Domingo " Mine, on the ridge 

 between Dark Canon and Baxter Basin, Gunnison Co., Col. ; 

 in which locality it is known as " mineral wool." It consists 

 of aggregates of small acicnlar crystals, forming matted, wool- 

 like masses in the cavities of a highly decomposed gangue rock 

 of siliceous material mixed with some calcite. It is dull, gray- 

 ish black in color, with occasional spots of iridescence, due 

 undoubtedly to a slight superficial oxidation. 



In procuring material for analysis, a lot of loose material sent 

 by Mr. Warren was slightly crushed and rubbed with water in 

 a mortar and poured off, the fine needle like crystals floating 

 off readily ; this was afterward purified by a re-treatment in 

 the same manner, and then subjected for a short time to the 

 action of dilute hydrochloric acid to remove the slight amount 

 of attached calcite. The material obtained in this manner ap- 

 peared under the microscope to be perfectly pure and homo- 

 geneous with the exception of a slight amount of gangue still 

 remaining. 



No crystalline form could be made out, and on account of 

 its peculiar nature no attempt has been made to determine 

 either specific gravity or hardness. Heated before the blow- 

 pipe it fuses readily without decrepitation ; in the closed tube 

 it gives a slight sublimate of sulphur only ; in the open tube it 

 gives off sulphurous acid and dense white fumes of oxide of 

 antimony ; heated strongly the antimony all volatilizes, leaving 

 a fused residue of. sulphate of lead, slightly colored by the iron 

 present ; on charcoal it gives the lead and antimony coatings, 

 and in the reducing flame with soda, a lead button. It is solu- 

 ble in hot, strong hydrochloric acid with evolution of hydrogen 

 sulphide. 



The analysis is as follows : 







Atomic ratios. 





Ag 



trace 







Cu 



trace 







Pb 



39*33 



-S-2'07='-'l90 ) 



•222 



Fe 



I'll 



-f- 56 = '032 J 



Mn 



trace 







Sb 



36-34 



-M20= 



•303 



S 



21-19 



-5-321 = 



•662 



Insoluble gangue, 



•52 







99-15 

 Dividing these atomic ratios by 222, we get : — 



Pb, Fe, = 1 =3 



Sb, 1-36 4-08 



S, 2-98 8-94 



Giving the formula :— (Pb, Fe),Sb 4 S„, or 3(Pb, Fe)S, 2Sb 2 S 3 . 



