II 



EXTRA-LIMITAL SPECIES, 453 



NITRE. 



Nitrate of Potash. CkaveUmd. 



Colour v/liite. In capillary crystals and crusts. Transparent to semi-transparent. Hard- 

 ness 2.0. Sp.gr. 1.94. Dissolves in water. Composed of nitrate of potash, and several 

 salts of lime, in variable proportions. 



With nitrate of lime and other salts, in the salt-petre caves of Kentucky, &c. 



PETALITE. 



Colour white or reddish white. In lamellar masses. Lustre glistening. Translucent. 

 Hardness 6.0. Sp. gr. 2.44. Before the blowpipe, it melts only on the edges. Composed 

 of silica 79.21, alumina 17.22, lithia.5.76. 



Bolton, Massachusetts. 



FINITE. 



Colour grey, greyish green or brown. Crystallized. Primary a hexagonal prism. Lustre 

 sometimes resinous. Opaque. Hardness 2.0 to 2.50. Sp. gr. 2.75 to 2.78. Whitens 

 before the blowpipe, and fuses on thin edges, but does not melt. Composed of silica 55.96, 

 alumina 25.48, potash 7.89, soda 0.39, peroxide of iron 5.51, magnesia with manganese 

 3.76, water 1.41. 



Lancaster in Massachusetts, and Haddam in Connecticut. It has been thought to be a 

 variety of mica. 



POLYMIGNITE. 



Colour blaick. In prismatic crystals. Primary a rhomboidal octahedron, the dihedral 

 angles of which are 136° 28', 116° 22' and 80° 16'. Lustre imperfect metallic, but brilliant. 

 Hardness 6.5. Sp. gr. 4.77 to 4.85. Infusible before the blowpipe. Composed of oxide 

 of titanium, zirconia, yttria, oxide of iron, etc. 



Beverly, Massachusetts (Shepard). 



PURPLE COPPER. 



Variegated Pyritous Copper. Cleaveland. 



Colour between coppcr-rcd and tombac-brown. Streak pale greyish black and shining. 

 Crystallized and massive. Primary a regular octahedron. Lustre metallic. Rather sectile. 

 Hardness 3.0. Sp.gr. 5.00. Melts before the blowpipe. Composed of copper 61.07, 

 sulphur 23.75, iron 14.00, silica 0.50. 



Chesterfield, Massachusetts ; Perkiomen, Pennsylvania. 



