388 Genth and Pen field — Contributions to Mineralogy. 



line plates from 30 to 80 mm in size. Professor Penfield says : 

 The form of the plates was not determined. The clear por- 

 tions show a biaxial interference figure with wide divergence 

 of the optical axes, about like muscovite. 



Color grayish white, slightly pinkish, luster vitreous to 

 pearly. Sp. gr. = 2'883. B.B. it fuses readily to a .brown 

 glass, coloring the flame intensely a deep red. The analysis, 

 being the mean of two or three determinations, gave : 



Si0 2 53-34 



A1„0 3 17-76 



Fe"„0 3 3-25 



MiiO 2-77 



MffO 0-05 



CaO 0-37 



Li o 4-60 



Na a O 1-55 



K 2 10-90 



H 2 0-65 



PI... 7-78 



103-02 

 Less O for Fl 3-28 



99-74 



The lepidolite plates were all more or less coated with 

 minute brownish white scales, which appeared to be a product 

 of the alteration of lepidolite. With great difficulty I picked 

 out 0-2563 grm. of pretty pure material which gave : 



Si0 2 52-91 



A1 2 3 21-15 



Fe-0 3 3-59 



MnO _. 0-94 



Li 2 2-19 



Ignition.. 5 - 97 



Fl, K 2 0, Na 2 0, etc not det, 



Therefore not cookeite, but lepidolite altered by hydration. 



10. Fttchsite. 



In a peculiar mica schist, consisting of a gray muscovite 

 with quartz in Habersham County, Ga., occurs associated with 

 chromite and interlaminated with gray muscovite a deep emer- 

 ald green mica in scales, sometimes from 10-12 mm in diameter. 

 Professor Penfield writes me about it as follows : " The f uch- 

 site does not show crystalline outline and the scales are small 

 for optical examination. I observed the following. The sec- 



