174 PHYSIOGRAPHY. CLASS II. 



> ~_.L. (Pr -f oc) 3 . Pr + oo. 



Fig. 71. All of them from the Rhine. 



Pr 1 



Cleavage. Slight indications parallel to 



and Pr -j- oo. Fracture small conchoidal, un- 



p 

 even. Surface P oo and _ a little rough, 



though even ; (Pr + oo) 5 smooth and uneven, 

 ( ' curved, the rest of the faces 



smooth and even. 

 Lustre adamantine, inclining to vitreous. Colour, 



emerald-green, verdigris-green, blackish-green, 



often darker on the surface. Streak green, a 



little paler than the colour. Translucent, often 



only on the edges. 

 Brittle. Hardness = 4-5 ...5-0. Sp. Gr. = 4-205, 



a crystallised variety from Rheinbreitbach near 



Bonn. 



Compound Varieties. Reniform, rather imper- 

 fect : composition imperfect columnar ; surface 

 drusy, and often of a darker colour. Massive : 

 composition as above. 



OBSERVATIONS. 



1. Formerly the varieties of di-prismatic Olive-mala- 

 chite were confounded with the present species, as has 

 been observed above (p. 166). Count BOURNON gives the 

 angle of the prism P + oo = 110, according to the pre- 

 ceding dimensions it would be = 109 28'. Yet the angles 



