Dr Rose mi Zinkenite, a New Mineral Species. 19 



Zinkentie. Mr Zinken himself has given an account of most 

 of its characters in his " Description of the Eastern Hartz? 

 along with some experiments by the blowpipe, proving the 

 mineral to contain sulphur, antimony, and lead, with a little 

 copper. I had delayed publishing the description of the spe- 

 cies, chiefly because I expected to receive a farther supply of 

 specimens, which might have allowed of a more exact deter- 

 mination of the regular forms. I am inclined to think that 

 the six-sided prism M is not a regular one, but an assemblage 

 of several individuals, after the same law, which occurs in ar- 

 ragonite. The exact admeasurement of the angles is very 

 difficult, particularly on account of the numerous longitudi- 

 nal striae. In some crystals, however, where these striae be- 

 gin only at some distance from the edge, I constantly found 

 the angle to exceed 120°, and the mean of two, the most dis- 

 tinct I met with, was 120° 39'. If no attention be given to 

 the striae, the angles will be found varying from 118J to 

 124J°. The crystalline form of each of the individuals, taken 

 separately, seems therefore to be a rhombic prism of 120° 39^ 

 [M) terminated by two planes (P,) making over the edge an 

 angle of 150° 36' with each other. They are set on the obtuse 

 edges of the prism, as in Fig. 4. The mode of their regular 

 composition is represented in Fig. 5. Two individuals are 

 joined to a third in such a manner, that their planes M' and 

 M fl coincide with the planes M and M 9 of that individual 

 to which they are attached. Supposing the individuals to be 

 prolonged beyond their faces of composition, a form will en- 

 sue, resembling a six-sided prism ; but on two faces, opposite 

 to each other, there will be slightly salient angles of 178° 3', 

 while the six angles are each equal to 120° 39'. Of the six ter- 

 minal edges between the faces marked P, four are equal to 

 165° 30' each ; and two others slightly differing from them cor- 

 respond to the obtuse salient angles formed on two of the la- 

 teral planes of the prism. The inclination of P on M is = 

 102° 42 7 . I found by measurement 102° 34/— 102° 49'. The 

 difference among the terminal edges would be decisive, if we 

 were not prevented from observing it, by the unevenness of 

 the faces. Generally I could measure only one of them, and 

 in no instance all the six ; they were found about 165° 40* to 



