156 PHYSIOGRAPHY. 



Crichtonite Cronstedite. 



Transylvania, &c. The only locality of the Crichtonite variety is the 

 department of the Isere in France, where it occurs in narrow vein 

 along with Anatase. 



The variety Ilmenite is found in the Ilmen mountains in the Urals. 



The black metallic crystals found accompanying the Spinel, Brucite 

 Rutile, &c., imbedded in Serpentine and white limestone at Amity 

 (N.Y.) belong to the present species. They have the form denominate) 

 Fer oligiste imitatifby HA.TJY. They are distinguished from Specula 

 Iron by color, fracture, streak, and a diminished specific gravity. Itals< 

 occurs in broad laminated, imperfectly hexagonal masses, at Washing 

 ton, (Conn.) imbedded in a vein of Quartz, traversing primitive rocks 

 and likewise in the eastern part of the same state. 



5. The Crichtonite presents us in its crystallization a nearer approxi 

 mation to perfect isomorphism with Specular Iron, than exists betweei 

 any other two species where the composition is equally diverse. 



CRONSTEDLTE. Rhombohedral Iron-Mica 



Primary form. Rhomboid, of unknown dimensions. 



Secondary form. Hexagonal prism. 



Cleavage, parallel with terminal planes of the hexagona 

 prism perfect; with the lateral, imperfect. 



Lustre vitreous. Color brownish-black. Streak darl 

 leek-green. Opake. 



Thin laminae are elastic. Hardness =2-5 nearly. Sp 

 gr. = 3-348. 



Compound Varieties. Reniform and massive : compo 

 sition columnar. 



1. Before the blow-pipe, it froths a little without melting: with bo 

 rax, it yields a- black, opake and hard bead. Reduced to powder, it ge 

 latinizes in concentrated muriatic acid. 



2. Analysis. 

 By STEINMANW. 



Silica 

 Oxhide of iron 

 Oxide of manganese 

 Magnesia 

 Water 



22-452 



58.853 

 2-885 

 5-078 



10-700 



