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ANNALS NEW YORK ACADEMY OF SCIENCES 



All intense pleochroi.sm possessed by this substance (very deep golden 

 3'ellow, bright yellow, to brownish yellow) differing entirely from that of 

 chrysotile or antigorite, agrees exactly with that characteristic of antho- 

 siderite — a satisfactory confirmation. 



It can be claimed for hardly any one of the examples given above that 

 more than an approximation to the truth has been presented. With the im- 

 perfection of both analyses and descriptions as published, each interpretation 

 yet calls for special tests of the very specimens of these micro-aggregates 

 used in the analyses, for confirmation: e. g., strong alkaline reaction or 

 other evidence of free magnesia in "picrofluite" and " diabantachronnyn," 

 and optical identification of prochlorite, chloritoid, etc., in the others. It 

 is certain that, in each of the specimens represented by these analyses, there 

 existed a certain intermixture of minerals the identity and exact proportion 

 of which should have been identified by the analyst. For such determina- 

 tion in any analysis certain accurate data are indispensable. In place of 

 the usual meagerness in description of physical properties, omission of 

 optical examination and common imperfection of the chemical analysis 

 itself, it is obvious that, in a proper investigation of any mineral, its complete 

 examination, physical and optical, should precede on the very specimen 

 used for the chemical analysis. Only under such conditions can exact 

 results be obtained from the universally heterogeneous materials which are 

 found in nature. It seems likely, however, from the results above shown, 

 through this old simple method, toward disclosure of latent mineral con- 

 stitution, that it may prove of advantage even if now applied to the series 

 of mineral substances whose chemical analyses have been published. 



