222 



Ml-. Levy on a New Mineral Species. 



crystals, flattened in a direction perpendicular to the axis of the 

 primitive rhomboid, and present the aspect of small flat tables 

 almost circular, with alternate re-entering and salient angles 

 on their edges. The form of the individuals which compose 

 these macles is represented by fig. 2 : all the planes are very 

 brilliant, except those marked d^, d% which are less shining, 

 but sufficiently so, however, to allow the use of the reflecting 



The angles are as 



d\ d' = 99° 22^ 

 The manner in which the two individuals are grouped in 

 the macles is very remarkable; their axes coincide, or are pa- 

 rallel ; and to have their relative position it is necessary to 

 suppose, that, being first in a parallel position, one of them 

 has turned 30° or 90° round the axis, instead of 60° or 180° 

 as is generally the case in the macles offered by crystals de- 

 i-ived from a rhomboid. The thickness of the two crystals is 

 the same, and their faces a ' are on the same level, and form 

 only one plane. 



Another remarkable fact to be noticed with respect to this 

 new substance, is its almost perfect isomorphism with Eudya- 

 lite. The primitive form of the last substance is an acute 

 rhomboid of 73° 40', differing only by 3' of the primitive form 

 of Mohsite : and moreover, out of the six modifications which 

 compose the crystal just described, — five, P, a\ c^, b^, d^, 

 occur on the variety of Eudyalite I have described in the Edin- 

 burgh Philosophical Journal for January 1825. 

 Fiff. 1. a Fig. 2. 



It seems from the appearance of the group of rock crystals 

 upon which this substance occurs, that there can be no doubt 

 that the specimen comes from Dauphiny. This circumstance, 

 added to the analogy- of some of the exterior characters, might 

 suggest the idea that Crichtonile and Mohsite belong to the 



same 



