42 F. R. Van Horn — Pisanite and Arsenopyrite. 



Chemical Composition. — Some five months after the min- 

 eral was collected, transparent specimens of both bine and green 

 varieties were submitted for analysis to Dr. W. R. Yeazey, 

 Assistant Professor of Chemistry at Case School of Applied 

 Science, and the writer is under great obligations to Professor 

 Yeazey for the analyses. Although the specimens had been in 

 a dry place so long after being collected, nevertheless some 

 moisture was noticeable when the mineral was broken. It 

 was, however, not deemed advisable to dry the specimens by 

 artificial means on account of the possible oxidation of the 

 iron, and also for fear of driving off some of the water of crys- 

 tallization which has been stated by Schaller* probably to take 

 place between 100°-110° C. 



Blue Pisanite. — Below is given under (1) the analysis of 

 the blue pisanite from Isabella, Tenn. Under (2) and (3} are 

 to be found analyses of pisanite by Dr. Sohallerf from the 

 Alma mine, Leona Heights, Calif. Under (4) is to be seen the 

 original analysis of the pisanite from Turkey by Pisani.^: 





(1) 



(2) 



(3) 



(4) 



so,. . 



.. 27-87 



29-28 



29-25 



29-90 



FeO .. 



.. 1718 



16-47 



5 46 



10-98 



CuO ... 



.. 8-50 



9-22 



17-95 



15-56 



MgO . . 



.. 0-47 







2-82 





h;o ... 



.. 46-47 



45-74 



45-21 



43-56 



100-49 100-61 100-69 100-00 



An inspection of the various analyses shows a very great 

 similarity between analyses 1 and 2. The water is evidently 

 too high in 1, and was probably due to a small amount of 

 moisture in addition to the water of crystallization. The 

 water in 4, on the other hand, is certainly too low, and was 

 probably determined by Pisani only by difference as the anal- 

 ysis totals 100 per cent, and this kind of analysis practically 

 always totals higher than 100. One interesting feature of the 

 Isabella mineral is the small percentage of magnesia. This 

 indicates the presence of a small amount of the very rare 

 cupromagnesite§ molecule, (Cu,Mg)S0 4 +7H„0, which is iso- 

 morphous with melauterite. 



Analyses of mine waters | from the region show the presence 



* Minerals from Leona Heights, Alameda Co., California, by W. T. 

 Schaller, Bull. Univ. of California, vol. iii, pp. 204-206, 1903. 



f Op. cit., pp. 206-207 



^Comptes Eendus, xlviii, 807, 1859. 



§ System of Mineralogy, Dana, p. 944. 



|| Preliminary Beport on the Mineral Deposits of Ducktown, Tennessee, by 

 W. H. Emmons and F. B. Laney, Bull. 470, U. S. Geol. Survey, p. 172, 1910. 



