248 DESCRIPTIONS OF MINERALS. 



where. In the United States it is found, in masses, at 

 Plainfield and Cummington, Mass. ; also abundantly at 

 Hinsdale, and on Stony Mountain, near Winchester, N. H. ; 

 at Blue Hill Bay, Me. The black exterior is a more or less 

 pure hyclrated oxide of manganese. 



Ehodonite may be used in making a violet-colored glass, 

 and also for a colored glazing on stoneware. It receives a 

 high polish and is sometimes employed for inlaid work. 



Spodumene. 



Monoclinic. I A 7=87, being near the angle of pyroxene. 

 Cleavage easy, parallel to I and i-i. Surface of cleavage 

 pearly. Color grayish or greenish. Translucent to sub- 

 translucent. H.= 6-5-7. C. =3*1-3 -19. 



Composition. (E 3 , Al) 9 Si 3 , in which E is lithium and 

 equals Li 2 , and 3 Li 2 is to Al as 1 : 4. This corresponds to 

 silica 61*2, alumina 29' 4, lithia 6*4 = 100. B.B. becomes 

 white and opaque, fuses, swells up, and imparts to the flame 

 the purple-red flame of lithia. Unaffected by acids. 



Biff. Resembles somewhat feldspar and scapolite, but 

 has a higher specific gravity and a more pearly lustre, and 

 affords rhombic prisms by cleavage. Its lithia reaction is 

 its most characteristic test. 



Obs. Occurs in granite at Goshen ; also at Chesterfield, 

 Norwich and Sterling, Mass. ; at Windham, Me. ; at Brook- 

 field and Branchville, Ct.; at Uton, in Sweden; Sterzing 

 in the Tyrol ; and at Killiney Bay, near Dublin. Cymato- 

 lite and Kfflinite are results of its alteration. 



This mineral is remarkable for the lithia it contains. 



Petalite. 



Monoclinic. Usually in imperfectly cleavable masses ; 

 most prominent cleavage angle 141° 30'. Color white or 



gray, or with pale-reddish or greenish shades. Lustre vit- 

 reous to sub-pearly. Translucent. H. = 6-6*5. G. = 2'o. 



Composition. Contains lithia like spodumene, and gives 

 the percentage — Silica Tt'9, alumina 17*7, lithia 3"1, "soda 

 1*3 = 100. Phosphoresces when gently heated. Fuses with 

 difficulty on the edges. Gives the reaction of lithia like 

 spodumene. 



Biff. Its lithia reaction allies it to spodumene, but it 



