308 The Shalka Meteorite. [No. 4. 



II. 



MlNERALOGICAL AND CHEMICAL EXAMINATION. 



Description. 



The stone is mainly composed of two distinct minerals, exclusive of 

 the external crust. The first of these is a light, ash-grey, soft mass, 

 very harsh and friable, like soft, friable ash-coloured sand-store, or 

 pumice, which sometimes runs in narrow whiter bands through the 

 mass. This ash-grey mass is thickly studded with specks and masses 

 of all sizes of a much darker greyish black mineral which has often a 

 bright metallic glance, and sometimes on the polished surfaces a silvery 

 lustre like some varieties of Diallage. Its powder is of a very light ash- 

 grey. 



Internally the darker mineral appears loosely aggregated, and some- 

 times slightly striated on the smoother surfaces, like minute fragments 

 of grey schorl ; and in the fractures fibrous and radiated like some 

 varieties of hornblende or actinolite. Its powder exactly resembles 

 that of the lighter coloured portions of the stone. 



The light, ash-grey mineral has also interspersed in it numerous 

 black shining specks, which to the magnifier in a bright light have the 

 bright glance of broken particles of black coal, or pitchstone ; the black 

 colour being somewhat bronzed in a strong light ; these assume all 

 shapes, and are sometimes partly globular like melanite garnets. They 

 rarely exceed in size a hempseed, but have at times a semi-crystallised 

 appearance and are sometimes agglomerated into minute carbonaceous 

 looking nests. 



Minute masses, of a very pale green, like olivine, are seen imbedded 

 in the dark grey masses above described, and some of these, particularly 

 at those parts of the stone which are but loosely aggregated, a r e seen 

 upon very close inspection by the magnifier to be a sort of olivine- 

 looking slag ; that is the mineral runs into a pale olivine-like glass, as 

 if it was in the act of crystallizing into olivine, or the olivine was in the 

 act of fusing to a rock. It is not, however, olivine but merely silicate 

 or silico-chromate of iron ; the entire absence of magnesia wholly ex- 

 cluding it from the class to which olivine belongs. 



The Crust. 



The black crust is in most parts closely adherent, but in some few 



