Genth.] ^4 [Oct. 2, 



gations. Some portions show the orthoclase cleavage. Color reddish- 

 white to flesh red. Sp. grav. = 2.528. Associated with a chloritic min- 

 eral, supposed to be glauconite, and magnetite. 

 The analysis gave : 



Loss by ignition = 0.67 



Si0 2 = 62.68 



Fe 2 O s = 0.23 



A1 2 = 20.90 



CaO = 0.15 



Na 2 = none 



K a O = 15.99 



100.62 

 14. Muscovite, pseudomorphous after Nephelite ? 



Dr. A. E. Foote brought last year from Wakefield, Canada, peculiar hex- 

 agonal crystals occurring there in the granular limestone, which he gave 

 me for analysis. The form seems to be hexagonal, the angle, between two 

 prismatic planes, measured 120° ; the larger crystal 20 mm broad and 18 mm 

 high shows the basal plane, but no pyramid, some of the smaller but less 

 perfect crystals appear to have a very small pyramidal plane also. 



Yellowish-white, finely crystalline, rarely some larger cleavage planes 

 are visible, which are probably calcite ; lustre pearly to slightly vitreous. 

 II = 3.0 ; spec. gr. = 2.755. 

 The analysis gave : 



C0 2 = 0.69 



H 2 = 4.25 



Si0 2 = 45.90 



A1 2 3 = 36.03 



Fe 2 3 = trace 



MgO = 0.68 



CaO = 0.92 



K 9 = 12.08 



100.55 



This is muscovite slightly contaminated with calcium carbonate. 



The form suggests a pseudomorph after nephelite. In the same range 

 at Diana, N. Y., as Geo. J. Brush has shown, nephelite is found altered 

 into gieseckite, which latter in all probability is only a more compact and 

 less pure variety of muscovite. 



15. Stilpnomelane pseudomorphs. Ankerite. 



Velvety coatings of a dark olive-green color and submetallic lustre, in 

 pseudomorphs after an unknown tabular mineral. The specific gravity, 

 taken in alcohol, was found to be, 2.957. Powtler pale olive-green. 



This variety has been analyzed in 1858, hy G. J. Brush (Am. Journ. Sc. 



