1880.] NATURAL SCIENCES OF PHILADELPHIA. 255 



It has the formula 

 and the symbol 



Kg, Tl , OJ3, U,.>. 



Before the blowpipe it fuses with intumescence at about 2.5 to 

 a black glass. It sometimes gives a red lithia color to the flame. 

 It is soluble in hydrochloric and sulphuric acids, with separation 

 of silica. In its pyrognostic properties it is thus similar to Annite, 

 although Annite is less fusible. Its oxj^gen ratio is that of Biotite, 

 but the absence of magnesia, and its physical and optical proper- 

 ties, distinguish it from that mineral. It occurs in good crystals 

 back of Pike's Peak, Colorado. Amazon-stone and Astrophyllite 

 occur in the vicinity. The material upon which this investigation 

 has been made was obtained from Dr. A. E. Foote, of this city. 



The name of Siderophyllite {(Tidrfpoq ifolkov) has been given in 

 allusion to the large percentage of iron which it contains. 



