368 



DESCRIPTIVE MINERALOGY. 



scratch glass. Before the blowpipe, it foams up at once, becomes browm, and by a continued 

 heat is brought to the state of a black opaque scoria. Its specific gravity is 2.41, and it con- 

 tains silica 78.25, alumina 12.75, alkaU 8.00, together with some oxide of iron and water.* 



SPODUMENE. 



[From the Greek dvoSos, as/ies ; in allusion to the change which it undergoes before the blo\vpipe.] 



Spodumene. CleaveUnd, P/nUips, Thomson and Shcpard. — Triphane. Haiiy and Bcndant. — Prismatic Spodu- 

 mene. Jameson. — Prismatischer Triphan-Spath. Mohs. 



Description. Colour gi-eenish white and greyish green. Streak 

 white. It occurs massive and in large granular concretions. Cleaves 

 in the direction of an oblique rhombic prism, which is its primary 

 form. Fig. 384. M on M' 93°. Fracture uneven. Lustre shining 

 and pearly. Translucent. Very easily frangible. Hardness from 6 . 5 

 to 7.0. Specific gravity from 3.11 to 3.19. Before the blowpipe, 

 it swells to a foliated reddish yellow mass, which on the smallest agi- 

 tation falls to powder. The outermost portions fuse into small glassy 

 globules {Thomson). 



Composition. Silica 66.49, alumina 25.30, lithia 8.85, oxide of iron 1 .45 (Arfwedson). 



Geological Situation. It occurs in primitive rocks, especially in granite. 



Saratoga County. Spodmnene was said by Dr. Steele to occur near Saratoga Springs, 

 associated with reddish feldspar, black mica and quartz ; but it may be that some other mine- 

 ral has been mistaken for this, as I am not aware that it has been found by any other mine- 

 ralogist. It occurs at Goshen, Massachusetts, and in the towns of Chesterfield and Sterling 

 in that State. It resembles pyroxene, but can easily be distinguished by its behaviour before 

 the blowpipe. 



PYROPHYLLITE. 



[From the Greek wu^, fire, and (puXXov, a lcaf.\ 



Pyrophyllite. Phillips, Thomsm, and M)/!i(App.) 



Description. Colour white or greenish white. It occurs in fibrous radiating masses, and 

 small elongated prisms whose form has not been determined. Cleavage indistinct, rectangu- 

 lar. Lustre pearly. Hardness 1.5. Specific gravity 2.80. Before the blowpipe, it spreads 

 out in a fan-like shape, and increases to twenty times its former bulk ; with borax, it forms 

 a green transparent glass. When heated with nitrate of cobalt, it assumes a blue colour. 



' Troost. J&umaX of the Academy of Natwfil Sciences of Philadelphia. V, 55. 



