510 PROCEEDINGS OF TEE NATIONAL MUSEUM. tol. 47. 



quartz, and muscovite. It was found at the locality in 1904, and 

 analyzed by the writer when beginning the study of quantitative 

 analysis. The results, given in column la in the table below, showed 

 it to have a composition distinctly different from that of any pre- 

 viously known mineral, although, because of lack of experience, it is 

 probable that they are not altogether accurate, some silica having no 

 doubt been weighed with the sesquioxides, and some manganese with 

 the calcium or magnesium ; but the boric acid, having been determined 

 by the writer's volumetric method,^ is probably exact. The matter 

 was then laid aside because of the pressure of other work, but when 

 the writer became connected with the Museum, it was taken up again. 

 To obtain a check on the previous analysis, all the mineral that could 

 still be broken from the specimens, amounting to less than half a 

 gram, was sent to Mr. J. E. Whitfield, of the firm of Booth, Garrett 

 & Blair, of Philadelphia, who has been doing considerable analy- 

 tical work for the Museum, and his results are given in column 1&. 



Meanwhile a mass of yellow plates, about 4 by 2 by 1 cm. in size, 

 was found at the quarry by Mr. J. Watts Mercur, jr., of WalUngford, 

 Pennsylvania. (U.S.N.M. Cat. No. 87233). Although showing no 

 planes defuiite enough for crystallographic measurement, this ma- 

 terial had the aspect of axinite, and the same specific gravity, 

 3.250. A clear fragment was sent to Mr. Whitfield for analyis, and 

 he obtained the results in column 2a; but as the boric acid seemed 

 rather low, probably owing to incomplete decomposition, two deter- 

 nmiations were made by the writer, and 5.98 and 6.09, average 6.04, 

 obtained (column 26). Using this value, the agreement with the 

 theory for axinite is so close as to leave no doubt that it is the mineral 

 represented. 



The question as to whether No. 1 was a new mineral, or only an im- 

 pure axinite, remained unsolved, so powder from both specimens was 

 submitted to microscopic examination. No. 2 showed a mean index of 

 refraction of 1.680, birefringence 0.008, and sign — , thus agreeing 

 with typical axinite. The greater part of No. 1 gave essentially the 

 same values, but scattered through this material could be seen 

 pinkish, pleochroic grains with a much higher index, 1.700, but still 

 lower birefringence, 0.005, showing, in fact, ultrablue interference 

 colors, also extinguishing straight and + in sign. These properties 

 identified it as zoisite, a mineral which had previously been reported 

 from the locaUty.^ Here, then, was the explanation of the difference 

 between analyses la and Ih, as well as their deviation from the theory 

 for axinite: the material is not homogeneous, but contains a variable 



1 Joum. Amer. Chem. Soc, vol 30, 1908, p. 1687. 



2 Cardeza, Proc. Acad. Nat. Sci. Phila., 1892, p. 194; discovered by Miss Mary S. Holmes. A small speci- 

 men of this mineral, not associated with axinite, collected by the writer about 1906, has also been added 

 to the Museum collection (Cat. No. 87234). 



