E. S. Dana— (Jhondroditc from the Tilly-Foster Iron Mine. 93 



Tahmc XIV. 

 Chondrodite. 



Humite. 



The two crystals described are the only ones which could be posi- 

 tively identified. It is very probable, however, that of those found 

 others also belong here, as they have much the same appearance and 

 habit. These crystals are all considerably altered, being generally 

 soft enough to be cut with a knife, and for this reason a chemical 

 analysis would be of little value. The color of the crystals is gray to 

 grayish-yelloM', and the material of which they are composed is never 

 pure, and often quite heterogeneous. In this respect they recall the 

 bi'own crystals described by v. Rath as occurring at Nya-Koppar- 

 berg. 



Whether brilliant crystals of the first tyjje exist, as they do of the 

 other types, must be left for the present undecided. 



4. On the Optical Properties of Chondrodite. 



In the preceding pages the question of the orthorhombic or clino- 

 rhombic crystallization of the chondrodite has not been discussed. In 

 fact, nothing was detected by the measurements sustaining any other 

 conclusion than that of Scacchi and vom Rath, that the crystals were 

 fundamentally orthometric. Still the hemihedral character of the 

 second and third types seem to point to a clinometric form, and this 

 is apparently supported by the optical characters obtained. The ma- 

 terial available for optical investigations was very scanty, and, with 

 the exception of one crystal, poorly adapted for the purpose. 



The crystal referred to was, properly, but the fragment of 

 what was originally a specimen of considerable size and beauty ; 



