OllDER VII. PRISMATIC EMERALD. 315 



Inclination of the face*. Inclination of the edge*. 



df on d = 151 46'. k on e = 130 8'. 



/' On / = 106 1 8'*. (A fragment from the Wernerian 



nn e> 1 2Q* Sfi' collection gave the analogous 



OH 6 = l^JT 00 . inclination of P on if nearly 



n' on = 143 10'f. 

 o' on o = 112 40^. a? (between e' and e) 



r' on r = 156 KX. on e = 154 37'. 



z/ on u = 134 14'. y on e = 101 55'. 



i' on i = 99 40'||. ;r on e = 141 4(K. 



The elevation of Fig. 54. is copied from the Traite of HAU Y, 

 Fig. 154., but the projection is taken immediately from the 

 original. The facets a, not mentioned by HAUY, follow 

 from the situation of the edges, those between a and d being 

 parallel to those between d and the prism /, while those be- 

 tween a and n are parallel to those between n and , or be- 

 tween n and the prism s. 



2. According to BERZELIUS, prismatic Emerald consists of 



Silica 43-22. 



Alumina 30-5G. 



Glucina 21-78. 



Oxide of Iron 2-22. 



Oxide of Tin 0-70. 



Before the blowpipe it intumesces in a strong heat, and 

 becomes white. If the heat be still farther increased, it 

 melts into a white enamel. 



3. JJothing as yet is known with sufficient accuracy of 

 the mode of its occurrence in nature. The first varieties 

 of it were brought by DOMBEY from Peru. It has been 

 found afterwards at Capao in the mining district of Villa- 

 llicca in Brazil, likewise in beautiful crystallised varieties. 

 It occurs there in a chloride slate, resting on sandstone, 

 along with prismatic Topaz, but is generally brought to 

 Europe in fractured crystals. 



* = 105 20 7 and 111 12'. f = 143 32' and 143 12'. 



= 114 8' and 113 40 7 . = 134 20'. || == 99 40'. 

 = 130 D 52'. According to PHILLIPS. H. 



