DOMAIN I. SIDEROUS. 



MODE I. SIDERITE. 



characters 6 Texture, generally crystalline, as in the saline 

 or primitive marbles ; the prisms sometimes in- 

 tersecting each other, so that it becomes difficult 

 to determine their figure*. The grains are 

 ^sometimes so small that it assumes a compact 

 appearance, in which case it passes into basalt. 



Hardness, basaltic, sometimes only marmoric. 

 Fracture commonly foliated, sometimes radiated, 

 tough. Fragments rather sharp. 



Weight, siderose : sometimes approaching the 

 barytose. 



Lustre, splendent, shining, between vitreous 

 and pearly. Opake; the green sometimes trans- 

 lucent on the edges. 



Colour generally black, sometimes of a green- 

 ish grey. 



Siderite sometimes composes entire mountains a 

 but more commonly occurs disseminated, or 

 forming veins or nodules, in granite ; or beds in 

 gneiss. 



This important substance, which is so widely 



Hornblende, disseminated, is the hornblende of the German 



miners; a barbarous term, which, like many 



* The crystals of siderite are of an oblong quadrilateral form, 

 while those of mica are hexagonal. 



