310 PROCEEDINGS OF THE ACADEMY OF [1880. 



Note on Philadelphite — a new mineral. — Mr Lewis gave a pre- 

 limiiiaiy description of a new verniiculite from near Wayne 

 Station on the Germantown Railroad, wliicli he proposed to call 

 ''■ Philadelphite." It occurs in plates of a brown color and talcose 

 lustre, existing as seams in an altered hornblende rock. When 

 heated, it exfoliates with great force to man}' times its original size 

 and becomes of a coppery bronze color. It was stated that while 

 exfoliating, it was able to lift over 50,000 times its own weight. It 

 had a hygroscopic power nearl}^ as great as that of chloride of 

 calcium. Its optical characters and its chemical composition were 

 given. 



Analysis of Philadelphite. — Mr. Reuben Haines contributed 

 the following analyses of Philadelphite. 



Specific gravity (determined in alcohol of 95 p. c.) 2.78-2.96. 



I. XL 



SiO^ 39.06 38.52 



re.,03 20.59 20.01 



AI2O3 14.75 14.82 



Fe,0 2.04 2.04 



CaO .99 1.08 



MgO 11.49 11.32 



MnO (traces) .... .... 



Li20 (traces) .... .... 



K,0 6.89 6.61 



Na,.0 .90 .64 



H,0 4.27 4.27 



F (traces) .... .... 



100.98 99.31 



Per cent, of hygroscopic water in I, 3.12 p. c. ; in II, 3.43 p. c. 



In these analyses the mineral was dried t.t 100° C, the hygro- 

 scopic water not being included in the determinations. Owing to 

 its very hygroscopic nature, it was found very diflicult to obtain 

 its weight at 100° C. accurately. It gains rapidly in weight while 

 being weighed upon the balance. Examples of its hygroscopic 

 power were given. The analyses were made l)y dissolving the 

 mineral in concentrated hydrochloric acid. Iron was estimated 

 volumetrically and the alkalies hj Smith's method effusion. 



