ORDER VII. PRISMATIC COKUNDUM. 305 



of intersection. The rest generally smooth and 

 even, Pr sometimes a little rough. 



Lustre vitreous. Colour asparagus-green, pass- 

 ing into greenish-white, olive-green and yellow- 

 ish-grey. Streak white. Transparent ... trans- 

 lucent. Blueish opalescence upon Pr and Pr -f- GO, 

 or in general if viewed in a direction perpendicular 

 to the short diagonal of the fundamental form. 



Hardness = 8-5. Sp. Gr. = 3-754, a transparent 

 asparagus-green variety. 



Compound Varieties. Twin-crystals : face of 

 composition perpendicular, axis of revolution par- 

 allel to one of the acute terminal edges of P. The 

 composition is frequently repeated on all the simi- 

 lar terminal edges, nearly as in Fig. 38., and easily 

 ascertained by the striae on the faces of Pr + oo, 

 which fall into one plane. The composition is very 

 common in the present species. 



OBSERVATIONS. 



1. According to SEYBERT, who analysed two varieties, 

 one from Brazil, and another from Haddarn, it consists of 



It remains unchanged if exposed alone or with soda to the 

 heat of the blowpipe, only the surface in the latter case be- 

 comes dull. It is difficultly, but perfectly fusible with 

 borax and salt of phosphorus. 



2. Also in this species the original repositories of some 



VOL. II. U 



