304 W. T. Sohaller — The Alunite-Beudantite Group. 



the isomorphous groups which are replaceable. The formulas 

 for these minerals then become : 



Alunite |"Al(OH).l, K,. 



Hamlinite [Al(OH),|,. Sr. 



Corkite [Fe(OH)J . Pb. 



[SO,],. 

 HPOJ, 



soj, 



so J,. 



Sr(P0 4 )J. 



[I'MPOjj. 



The general formula is written : 



[R'"(OH)J,R".[M],[M,]. 



where K"' = Al, Fe'". 



R" = K„, Na„, H„ Pb, Sr, Ba. 



M = S0 4 , HPO„ HAs0 4 , Pb^P0 4 , Sr M P0 4 . 



The entire group then consists of the following minerals ; 

 Sulphates.— Type formula [R'"(OH),],.R', or R".[SOJ,.[SOJ,. 



Alunite -. [Al(OH),' 



Natroalunite [Al(OH), 



Jarosite [Fe(OH), 



Natrojarosite. [Fe(OH), 



Plumbojarosite [Fe(OH).,' 



Carphosiderite [Fe(OH)," 



K, 



Na, 



K 2 . 



Na.. 



Pb. 



H„. 



[soj,- 

 rsoj,- 

 soj,- 

 [so 4 ] 2 - 

 [soj,- 

 [soj,- 



soj, 



[ so;; 



soj, 

 so 4 j, 



Phosphates.— Type formula [R'"(OH),]„.R".[R'POJ,.[R"(P0 4 ) J. 



Hamlinite 



Plumbojarosite 



Gorceixite 



Florencite 



[Al(OH),l,. Sr. 



'Al(OH),],. Pb. 



AJ(OH),|, Ba. 



[Al(OH)J, Ce, 



HPOJ, [Sr(P0 4 ),j. 

 HPOJ,. [Pb(P0 4 )J. 

 HPOJ,. [Ba(P0 4 )J. 



[CexPOJ,[Ce ?< (P0 4 ),]. 



Sulphate - Phosphates.— -Type formula [R'"(OH)J 6 . R". [SOJ, 

 [R"(POJJ. 



Beudantite [Fe(OH)J 6 . 



Corkite [Fe(OH),"|,. 



Svanbergite [Al(OH)J 6 . 



Hinsdalite [Al(OH),],. 



Harttite 



j [Al(OH) 



Pb. 

 Pb. 

 Sr. 

 Pb. 



Sr. 



[S0 4 

 [S0 4 

 [SO, 



[so 4 ; 

 [so 4 j 



Pb(As0 4 ),]. 

 Pb(P0 4 ),]. 

 [S'-(PO,)J. 

 Pb(P0 4 ),j. 



[so 4 j, 



(2![Al(OH)J, Sr. [HP0 4 ], LSr(P0 4 )J( 



Note. — Pastreite bas been determined as jarosite (Bull. soc. franc. Min- 

 eral., vol. xxxiii, 1910, p. 130), the earlier analysis being wrong. 



Chemical Laboratory, 

 United States Geological Survey, 

 Washington, D. C. 



