No. 75.] 



143 



The micas with a single axis, so far as I have examined them, are 

 usually more easily fusible than those with a double axis. In thin frag- 

 ments they curl up under the blowpipe and fuse into a vermicular en- 

 amel, varying in color with the specimen. The following belong to, 



HEXAGONAL OR MONOAXIAL MICA. 



Forshees mine. Orange county. Optic axis single ; rather difficultly 

 fusible. 



Copper colored mica, from Edenville, Orange county. Optic axis 

 single ; fuses into a dark enamel. 



Silvery mica, from Rossie, St. Lawrence. Optic axis single ; fuses 

 into a white string. 



Mica, from Vrooman lake, Jefferson county. Optic axis single. 



Mica, from Governeur, St. Lawrence county. Optic axis, single. 

 In thin plates it fuses into a string of a white color and high lustre. 



Copper colored mica, from Edwards, St. Lawrence county. Crys- 

 talized in six-sided tables, sometimes 5 or 6 inches in diameter ; optic 

 axis single ; fuses with difficulty into a white mass ; angles of the 

 crystals about 120^ ; lustre metallic ; plates sometimes curved. 



Silvery mica, from Edwards. Crystallized in six-sided tables ; optic 

 axis single ; fuses rather more easily than the preceding. 



The brown mica, from Jefferson county, New- York, has been ana- 

 lyzed by Meitzendorff, whose average results are thus stated by Ber- 

 zelius, {Arsb. 1843, p. 211,) silica, 41"30; alumina, 15*25; peroxideof 

 iron, 1-77 ; magnesia, 28'79 ; potaj-h, 9*70; soda, 0'65; fluoric acid, 

 3'30; loss by ignition, 0*28. It thus agrees very nearly with Prof. 

 H. Rose's analysis of magnesian mica from Siberia. Alger^s Phillips, 

 619. 



ORDER III. GLUCINA. 



CHRYSOBERYL. 



(Mineralogy of New- York, page 375.) 



To the extensive series of compound crystals figured in the Mineral- 

 ogy of New- York, I have to add a few others. For the ability to do 

 this, I am indebted to Dr. Leonard, of Lansingburgh, N. Y., who has 

 been uncommonly successful in his exploration of the Greenfield local- 

 ity. He has obtained from thence specimens of extraordinary size and 

 beauty. Many of them exhibit the forms which I have heretofore 



