Genth and Penfield — Contributions to Mineralogy. 205 



These results indicate the presence of a small quantity of basic 

 hydrogen, replacing calcium and magnesium ; taking this view, 

 the following closely agrees with the results of the analyses : 

 (H 2 CaMg) 3 As 2 8 +6H 2 0, which is the composition of picro- 

 pharmacolite. 



6-_ HoO ; 108 22-34 per cent. 



0-25 " basic... 4-5 0-93 



1-95 CaO 109-2 22-59 



0-19 MgO :. 31-6 6-54 



1-— Aso0 5 230- 47-60 



483-3 100-00 



II. Analyses of crusts mixed with globular aggregations : 



a. b. c. d. Mean. Mol. ratio. 



H 2 24-38 24-11 24"25 24-58 1-35 6-5 



CaO 20-29 19-78 19-27 19-22 1964 351 1-7 



MgO ... 8-35 8-15 8-67 8'48 8"41 210 1 



Mn0 2 .. 0-14 0-29 0-41 0"29 



As 2 5 .. 47-74 47-74 2-08 1 



100-37 



These analyses also show the replacement of calcium by 

 hydrogen like the first two, and also a larger percentage 

 of magnesia, while agreeing with the formula of picropharma- 

 colite. 



III. The material of analyses III was, on account of being 

 interrupted with my work, placed for a month over H 2 S0 4 . 

 It will be seen from the analyses given below, that it contained 

 a still larger percentage of magnesia, and that in drying, one of 

 the six molecules of water was lost. 



a. b. Mean. Molecular ratio. 



H 2 20-50 20-19 20"35 1-13 5'14 



CaO 17-31 16-87 17-09 0-31 T41 



MgO 11-61 11-48 11-54 029 1-32 



Mn0 2 0-29 0-34 



As 2 5 50-60 50-51 50-56 0-22 1 



100-28 99-39 99-54 



6. Pitticite. 



At the Clarissa Mine, Tintic District, Utah, a mineral has 

 been found occurring in cryptocrystalline masses, largely inter- 

 mixed with limonite, and forming coatings made up of minute 

 botryoidal groups, seldom over l mm in size, and having a lus- 

 trous crystalline surface. H = 3'5. Luster resinous to waxy, 

 color brown to dark yellowish brown. Only with great diffi- 

 culty comparatively pure material could be selected for the 

 analysis which gave : 



