16 i Outlines of the Mineralogy and Geology 



SPECIES XL—SCHddLSTO.YE 



Subspecies I. — Chelmsfordite. 



Exter7ial Characters. 



Its colours are white, grey, green, and red. Of white, it oc- 



curs snow white, and greenish white ; of grey, ash grey and blu- 

 ish grey ; of green, siskin green ; and of red, rose red. White 

 is the most common colour, the others occur in veins or clouds. 



Its lustre is glistening and pearly, glimmering and resino- 

 vitreous, or dull. 



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It is translucent at the edges ; some specimens are translucent. 

 It is amorphous, and crystallized in prisms which are either 



rectangular, or slightly rhomboidal. The lateral edges are.some- 

 times truncated, and the acute and opposite edges of the rhomboi- 

 dal prism, are sometimes so deeply truncated, that an imperfect 

 hexagonal prism is produced. The surface of the crystals is 

 deeply longitudinally striated, and transversely rent. The crys- 



tals are variously aggregated, sometimes they are longitudinally 



united, but they are generally promiscuously intersecting. 



The streak is greyish white. 



It sometimes occurs in straight lamellar, and in prismatick im- 

 perfect distinct concretions. , 



It is semi hard, passing into hard. 



The fracture is splintery, fine grained uneven and imperfect- 

 ly foliated. The crystals present a single cleavage parallel to 

 the bases of the prisms, but generally the cleavage is indistinct. 



It is brittle. 



It is easily frangibie. 



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