Prexcott — Ilvaitefrom Shasta Co., California. 



15 



b ^ s (010^120) 

 m^s (110^120) 

 m A m in (110/vllO) 

 o ^ r (111 A 101) 

 o ^ o m (111^111) 

 (890 /v 120) 



Measured 



36° 



40' 



20 



09 



66 



45 



20 



7 



40 



28 



16 



■15* 



Theoretical 



36° 



52' 



19 



27 



67 



22 



20 



7 



40 



15 



16 



16 



minerals of similar appearance. Before the blowpipe it fuses 

 readily with slight intnmesence to a magnetic globule, yields 



a small amount of water at high temperature in a closed tube 

 and is readily soluble in hydrochloric acid, giving a gelatinous 

 residue upon evaporation. 



Moss, Hillebrand,f Hoffman,:}: 



Shasta Co., Owyhee Co., Vancouver Theo- 



Cal. Idaho Island, B. C. retical 



Si0 2 28-09 29-16 29'81 29*3 



A1 2 3 -32 -52 0-16 



Fe 2 3 20-80 20-40 18-89 19"6 



FeO 29-93 2-9-14 32*50 35'2 



MnO 3*24 5-15 2'22 



CaO 15-89 13-02 13-82 13*7 



MgO -18 -15 -30 



Na 2 -08 



Cr.O, -13 



H a O 1-62 2-79 1-62 2-2 



Total 100-20 100-41 99'32 100*00 . 



* This agreement is accidental, as the recorded value is the average of 

 many readings on several faces, 

 f Bulletin U. S. G. S. No. 207, p. 45. 

 % Vol. 5, Annual Eep. Geol. Survey of Canada, 1889-90. 



