PHYSIOGRAPHY. 33 



Apatite. 



Cleavage parallel with the planes of the primary form, 

 that parallel with the base obtained with most difficulty. 



Fracture conchoidal, more or less perfect, uneven. 



Surface, the secondary faces generally very smooth ; the 

 primary lateral ones striated in a longitudinal direction. 

 Sometimes all the edges are rounded. 



Lustre vitreous, inclining to resinous. Color white, fre- 

 quently violet-blue, mountain-green, or asparagus green ; 

 also yellow, grey red and brown colors, though none of 

 .them are bright. Transparent Or translucent. A bluish 

 opalescence appears upon the faces parallel to the principal 

 axis in some crystals, particularly the white varieties. 



Brittle. Hardness = 5-0. Sp. gr. = 3-225 (asparagus- 

 green crystals from Spain) ; =3' 180, from Salzburg. 



Compound Varieties. Implanted globular and reniform 

 shapes : composition imperfectly columnar ; faces of composi- 

 tion rough. Massive : composition granular, individuals of 

 different size, not impalpable; faces of composition uneven 

 or rough. 



1. Several varieties of the present species which are decidedly sepa- 

 rate from others and connected among themselves, were formerly con- 

 sidered as forming two or even three distinct species. The distinctive 

 marks between them, however, are so slight, that they are incapable of 

 being indicated with certainty, and it would therefore be superfluous to 

 attempt their explanation. 



2. Certain varieties are phosphorescent upon ignited charcoal and be- 

 fore the blow-pipe ; in particular those crystals which are terminated by 

 a single plane, some of which phosphoresce when rub"bed with hard bod- 

 ies. In a very strong heat of the blow-pipe, the edges and solid angles 

 are rounded off; but it does not melt without addition. With borax, it 

 dissolves slowly into a clear glass. With salt of phosphorus it dissolves 

 in great quantities, affording a transparent glass, which, when nearly 

 saturated, becomes opake in cooling, and presents crystalline faces, sim- 

 ilar, but less distinct than phosphate of lead. Apatite has been artificial- 



