L86 Ford and liradh // — Pseudomorphx after Stibnitc. 



Two complete analyses and one partial analysis were made 

 of one sample, which consisted of small crystal fragments. The 

 results were as follows : 



Specific gravity, 4'906. 



I II III Average 



Sb.,O r 85-43 85-04 85*53 



CaO. 0-64 9'69 9-81 9-71 



H„0 4-84* 4-83* 4-73f 4-80 



Total.. 99-91 100-10 100-04 



* Loss on ignition. \ Direct determination. 



It happened that this analysis yielded quite definite molecular 

 ratios. The formula, however, which was derived was quite 

 unusual and was very different from that of any known antimo- 

 nate. It was thought, therefore, that the ratios might be acci- 

 dental, and a second analysis was made in order to decide this 

 point. The second sample was taken from the lower end of 

 one of the crystals, and the results of its analysis follow : 



IV 



Sb 2 G 90-43 



CaO°. 7-30 



H 2 ....' 3-83 



Total 101-62 



By the comparison of the analyses of the two samples it 

 will be seen that the composition is not uniform, and so, 

 consequently, no definite formula can be assigned to the 

 material. In the analysis the antimony has been calculated as 

 the pentoxide, but the question of the state of oxidation of 

 the antimony is a difficult one to decide. The fine powder of 

 the mineral was partially soluble in hydrochloric acid, and this 

 solution contained antimonic antimony since it liberated iodine 

 from a potassium iodide solution. Since the mineral is only 

 partially soluble in hydrochloric acid, and in view of the fact 

 that when the antimony found in analysis IV is all calculated 

 as Sb 2 5 the summation of the analysis shows an excess, the 

 assumption is natural that the mineral contains the lower oxide, 

 Sb„0 4 , as well. Further, if the mineral contains Sb 2 B in the 

 usual form it should liberate oxygen when ignited, being 

 reduced to Sb 2 4 . That this does not take place is proved by 

 the agreement between the determinations of water made by 

 the two different methods. The conclusion arrived at is that 

 the mineral is not a definite compound, but is composed rather 

 of amorphous material with varying composition. 



Mineralogical Laboratory of the Sheffield Scientific 

 School of Yale University, New Haven, 

 June 1st, 1912. 



