W. T. Schaller — Mineralogical Notes. 153 



suspended from the balance arm. The result obtained is 3*40, 

 which shows that the figure previously given, about 3 - 15, is 

 entirely too low. 



The sample was air-dried for several weeks and then anal- 

 yzed, with the results given below : 



Eatio. 



P„0 6 43-45 .306 1-00 



Fe 2 G 3 38-36 240 



Mn„O s 12-08 76 <- 1-06 



CaO 1-37 24 



H _. 4-82 268 



Insol -. -19 



MgO,Na 2 0,Li 2 0, trace 



100-27 



The ratios agree fairly closely with those found in the 

 original paper, giving as the formula of the mineral 

 (Fe,Mn) a O s .P 8 6 + H a Or In the South Dakota mineral, the 

 iron greatly predominates over the manganese. 



Connecticut. — A small specimen from the well known min- 

 eral locality of Branchville, Conn., was kindly furnished the 

 writer by the late Prof. Penfield. This specimen is coated 

 with a purple mineral which in its optical properties as seen 

 under the microscope agrees well with purpurite. 



Only a very small amount of material (0-0197 gram), which 

 was fairly pure, could be obtained for analysis. A direct de- 

 termination of the water was made but the phosphoric acid had 

 to be determined by difference. The results obtained are as 

 follows : 



Eatio. 

 Fe 0, 27 17 



Mn 2 O s ._ 23 15 



P 2 6 [44] 31 



HO 6 33 



100 

 The ratios are nearly 1:1:1, giving the same formula as before 

 namely : (Fe,Mn) 2 3 .P 2 5 +H 2 0. 



Considering now the three analyses of purpurite from North 



Carolina, South Dakota and Connecticut, it is seen that the 



iron and manganese vary reciprocally, so that purpurite is, 



without question, an isomorphous mixture of 



Fe„0 3 .P 2 B + H„0. 



Mn 2 3 .P 2 6 + H 2 0. 



In the South Carolina mineral, the manganese predominates ; 

 in that from South Dakota, the iron predominates, while in the 

 Connecticut mineral the iron and manganese are present in 



