W. P. Head den — New Phosphate from South Dakota. 415 



Art. L. — A new Phosphate from the Black Htlls of South 

 Dakota ; by W. P. Headden. 



The mineral described in this note was found in the Nim- 

 rod, now called the Riverton, lode, near Harney City, Pen- 

 nington Co., South Dakota. It occurs in the granite common 

 to the district, in kidney-shaped masses, some of them weigh- 

 ing upwards of fifty pounds, but they are not numerous. 

 Externally they are dark brown, due to oxidation which has 

 taken place, in some cases, to the depth of a quarter of an 

 inch, in others only on the surface. These masses enclose a 

 few crystals of white mica, but are not penetrated by crystals 

 of this mineral which often adhere to the surface. Some of 

 them show small seams of an almost white mineral with two 

 cleavages nearly at right angles to one another ; its composi- 

 tion has not been determined. It is easily recognized under 

 the microscope, especially in polarized light upon which it acts 

 strongly, while the inclosing mineral has no effect upon it. In 

 places there are dark patches visible only in pieces thin enough 

 to transmit light. The mineral is amorphous and by reflected 

 light has a dark brown color ; by transmitted light in very thin 

 pieces it is a yellowish brown, in thicker ones a brown color. 

 It has a resinous-vitreous lustre, an uneven to conchoidal frac- 

 ture and no cleavage. In thin flakes it is translucent to trans- 

 parent. Specific gravity, 3-401 ; hardness, 5*5 and is brittle. 

 It is readily soluble in acids, fuses easily in the flame of a 

 candle and reacts for manganese, iron and soda, before the 

 blowpipe. 



The material for analysis was carefully selected, only such 

 pieces being taken as were thin enough to show by transmitted 

 light that they were free from the dark patches and macro- 

 scopic seams. The results were as follows : 





I. 



II. 



in. 



IV. 



V. 



Mean. 



Oxygen. 





P 2 5 ... 



38-61 



38-22 



38-45 



38-49 



38-86 



38-52 



•217 2-17 



MnO ... 



29-74 



2974 



28-97 



30-08 





29-64 



•0668^| 



CaO . . . _ 



7-70 



7-66 



7-66 



7-08 



7-28 



7-47 



0213 





A1 2 3 .. 



9-94 



10-34 



10-09 





10-14 



10-13 



•0472 





FeO .... 



383 



4-14 



4-01 



4-00 





4-00 



•0089 





MgO ... 



0-14 





0-16 







0-15 



•0006 ^ 1*917 



Na 2 .._ 

 K 2 0_... 



5-52 



0-30 



E f 



5-70 



5-68 



1 :':":": 



5-52 

 0-30 



•0142 

 •0005 





Li 2 



trace 





trace 









trace 







H 2 0..._ 



4-15 







4-43 











4-29 



•0382J 



CI 



0-11 





Dot det. 









01 1 





E 



trace 











trace 





IqsoI 



0-14 



.... 



0-18 



.... 



.... 



0-16 







0-91 



100-18 



99-65 



100-29 



