a New Mineral Species. 317 



the foregoing simple forms, and to Fig 13, which, moreover, 

 contains the alternating faces of a very flat four- sided pyramid, 

 p, p, which allows of no measurement. 



Cleavage. Pretty distinct, parallel to the rectangular four- 

 sided prism, m. In other directions, there is small and imper- 

 fect conchoidal fracture ; sometimes it is uneven. Surface of 

 P 

 2 and P-foo generally smooth, the other faces curved and 



without lustre. 



Lustre vitreous. Colour greyish-white. Semi-transparent, 

 generally only translucent. Streak white. 



Brittle. Hardness — 4.0 . . . 4.5, nearer the latter. Sp. gr. 

 = 2.710, of a number of small crystals, forming together, 243 

 milligrammes. 



Observations. 



1. Among a great number of interesting minerals from the 

 neighbourhood of Glasgow and Dumbarton, in the possession 

 of Mr Edington of Glasgow, with the inspection of which I 

 have been lately gratified, I observed some crystals disposed 

 in the cavities of Thorn sonite, which at first I expected would 

 belong to that species ; but I soon found that their faces could 

 not be identified with those mentioned in the descriptions of 

 it, as given by Messrs Brooke* and Phillips, f Mr Edington 

 had the kindness of entrusting me with the only specimen of 

 the substance which I could discover in his collection, and to 

 which the preceding description refers. It is in compliment 

 to that gentleman that the name of Edingtonite is here pro- 

 posed for designating the species. 



2. The regular forms of Edingtonite, even if we do not at- 

 tend to the interest attached to every novelty, are highly de- 

 serving of notice on account of their forming the only second 

 instance, among natural crystals, of hemi-pyramidal forms 

 with inclined faces ; the first example observed being the spe- 

 cies of pyramidal copper-pyrites. Hemi-pyramidal forms are 

 in general very rare ; the pyramidal scheelium-baryte of Mohs, 

 (tungstate of lime,) is the only well authenticated instance 



* Ann. of Phil. vol. xvi. p. 193. 

 -f- Mineralogy^ p. 39. 



