W. M. Bradley — Analysis of the Mineral Neptunite. 15 



Art. III. — On the Analysis of the Mineral Neptunite 

 from San Benito County, California ; by W. M. Bradley. 



The rare mineral neptunite was discovered early in 1907 

 near the head waters of the San Benito River in San Benito 

 County, California. It was associated in its occurrence with 

 the new mineral benitoite, a barium titano-silicate, and at first 

 was thought to be a new species and received the provisional 

 name of carlosite.* 



A crystallographic and optical study of these neptunite 

 crystals has recently been published by Prof. W. E. Ford,f 

 and the present chemical investigation is supplementary to 

 that article. The mineral has previously been found only in 

 the Julian ehaab district, Greenland, and two analyses of the 

 mineral were made from material obtained from this locality ; 

 one by Flink;};, and the other by Sj6strom.§ The results of 

 their analyses follow : 



Si0 2 Ti0 2 FeO MnO CaO K 2 Na 2 MgO 

 Flink 51-53 18*13 10*91 4'97 — 4'88 9*26 0*49 = 100'17 



Sjostrom 51'93 17'45 1023 5'32 0'71 5'7l 9'63 — =100'98 



The material used for the present analysis was obtained from 

 the Brush Collection and was of ideal purity, it being selected 

 from crystals similar to those used for crystallographic meas- 

 urements. 



Method of Analysis. — A very brief outline of the analytical 

 methods employed may here be given. The mineral was 

 fused with sodium carbonate and silica determined in the 

 usual way. The filtrate obtained after the removal of the 

 silica was used for a basic acetate precipitation, and the pre- 

 cipitate thus obtained eventually fused with acid potassium 

 sulphate. The titanium was precipitated in a rather strongly 

 acidified acetic acid solution in the presence of sodium acetate 

 and S0 2 water by boiling the solution from three to five min- 

 utes. In the filtrate from the basic acetate precipitation the 

 manganese was precipitated as Mn0 2 by bromine water in the 

 presence of sodium acetate, and after dissolving in strong S0 2 

 water was reprecipitated as ammonium-manganese phosphate. 

 Calcium and magnesium were determined by the common 

 gravimetric methods, and the alkalies by making a Smith's 

 fusion. Ferrous iron was determined by dissolving the mineral 



*Univ. Calif. Pub., v, 9, pp. 149-153, 1907. 



fThis Journal, (4), xxvii, 235, 1909. 



JG. For. Forh., xv, 196, 467, 1893; Zeitschr. Ki\, xxiii, 346, 1894. 



§G. For. Forh., xv, 393, 1893. 



