a new Mineral Species. 3 



The following account contains the characters ascertained in 

 the two specimens. 



The forms of Sternbergite belong to the prismatic system. 

 Its fundamental form (Plate I. Fig 8.) is a scalene four-sided 

 pyramid, having edges of 128 49', 84 28', and 118 0'. The ra- 

 tio of its axis and diagonals a : b : c, is 1 : ^/\ .422 : v/0.484. 



The specimens contained the following secondary forms, 

 P oo (a) ; P (/) ; P + 1 (g) = 122 17', 68 22', 146 34' ; 

 (P?) 3 (d) = 92 28', 107 17', 131 17' ; Pr +1(6) = 61 35' ; 

 i Pr + 3 (c) - 13 36' ; Pr + oo (i) ; 1 P 73 (h) - 153 2'. 



The combinations observed are, 



1. P oo.(P?)\ P+l.|Pr +3.P r "+ oo . Fig. 1. 



2 . P_oo.|P7 3.P.(Pr)'.Pr +1. Pr + 00. Fig. 2. 



There were traces of planes taking off the edges between d and 

 d', which I could measure. The measurement gave for the base 

 of the pyramid d, by approximation 81 12'. 



3.P oo,|P7--3.Pr-J-l . (Pr) 3 . P+l.fPr + 3. Fig. 3. 



The edges between b and two adjacent faces of d are pa- 

 rallel. 



4. P 00 . P . Pr + 1 . (Pr) 3 . P + 1. | Pr + 3. Fig. 4. 



The crystals are very much compressed between a and a. They 

 assume the aspect of Fig. 5., or of a six-sided table with two 

 angles of 119j, and four of 120|. The faces i are usually 

 smaller than those marked m, which in fact are nothing but a 

 succession of planes, having the inclination of/ and g. 



Cleavage is highly perfect, and easily obtained, paraUel to the 

 face a ; in other directions the laminae may be torn asunder, like 



A 2 



