106 Penfield and Foote — Composition of Tourmaline. 



The filtrate from the silica was evaporated to dryness, mois- 

 tened with hydrochloric acid and repeatedly evaporated with 

 methyl alcohol to remove all possibilities of boric oxide being 

 precipitated with the bases and thus increasing their weight. 



For the determination of the alkalies the Smith fusion was 

 employed and, after removal of ammonium salts, the residue 

 was treated with acid and methyl alcohol and evaporated to 

 remove any borate that might possibly be present. Lithium 

 was separated by the Gooch method of boiling with amyl 

 alcohol,* and was finally weighed as sulphate. 



It was proved by careful qualitative tests f that the iron 

 was ferrous, and that, at the most, not more than traces of ferric 

 iron could be present. This statement holds good not only for 

 the varieties analyzed, but for all the varieties of black tourma- 

 line which were accessible to us. 



Selection and preparation of material. — One of the varieties 

 selected for analysis was the white or colorless tourmaline from 

 De Kalb, St. Lawrence Co., New York. This was chosen 

 because according to the analysis of Riggs it represented 

 almost the extreme type of a magnesia tourmaline, and, 

 containing almost no iron, there could be no appreciable error 

 from a failure to estimate that constituent correctly. The 

 material was derived in part from a specimen in the Brush 

 Collection and in part from specimens collected by one of us 

 (Penfield) while connected with the U. S. Geological Survey. 

 The clear, colorless, glassy material was most carefully selected 

 with the aid of a lens, ground and sifted to a uniform grain ? 

 and suspended in methylene iodide. The specific gravity was 

 uniform, and the portion used for the analysis floated at 3*065 

 and sank at 3*033. As an additional precaution the grains 

 were treated with a mixture of hydrochloric and hydrofluoric 

 acids, which have almost no action even on finely pulverized 

 tourmaline, in order to remove any possible traces of adhering 

 calcite, tremolite or pyroxene, although these were not seen 

 nor believed to be present. It may be stated concerning the 

 final product that probably it was as pure as it is possible to 

 get a mineral substance. 



Another variety selected for analysis was from the feldspar 

 quarries at Haddam Neck on the Connecticut River. Wonder- 

 ful tourmalines have recently been obtained from this locality, 

 and they are already well know to most collectors. We are 

 indebted for our supply of material to Mr. Ernest Schernikow 

 of New York, who generously placed at our disposal an almost 

 unlimited supply of crystals of gem quality. We selected 

 small prisms, 2 to 4 mm in diameter, of a uniform rather pale 

 green color. They were of ideal purity, perfectly transparent 



*Amer. Chem. Jour., ix, p. 33. 

 f See note, p. 124. 



