40 Mr. W. Phillips's Remarks 



stance which we have been considering should be ranked as 

 a pseudomorphous production, a i-egiilarly crystallized chalce- 

 dony, or a iie'iii substance, — we therefore deemed it right to 

 state them. 



Devonport, Nov. 25, 1826. 



XII. Remarks on the Crystalline Form of the Haytorite. By 

 W. Phillips, F.G.S. 8,-c*- 



T HAVE received from the writer of the foi'egoing commu- 

 -■- nication, and from the other gentlemen who are therein 

 mentioned, several crystals of the substance to which they have 

 given the appropriate name oi Haytoritc. 



It has only been found in regular crystals, which in general 

 are well defined, the edges being sharp, and the planes for the 

 most part brilliant. In dimension they vary from the size of 

 a pin's head to an inch in diameter : three or four minute cry- 

 stals are colourless and almost perfecdy transpai'ent ; but in 

 general their colour passes from pale brownish yellow, (in 

 which case they are translucent,) to deep brown and opaque. 



The crystals, however, have rai'ely been found isolated, 

 being commonly grouped together in such a manner as to 

 shon- only about one half of the crystal, but they are easily 

 separable ; the planes of separation are bright and frequently 

 somewhat iridescent on the surface. 



I have in vain attempted to discover a regular cleavage^ 

 which rarely is absent in crystallized minerals ; and it is re- 

 markable that the surface produced by breaking a crystal in 

 anv direction, is almost totally devoid of lustre, having com- 

 pletely the aspect and fracture of chalcedony : and this takes 

 place even in the almost perfectly transparent crystals, which 

 lose immediately that character, assuming the same degree of 

 translucency as is commonly possessed by chalcedony, when 

 viewed on the fractured surface. Specific gravity of two 

 translucent crystals taken by my friend S. L. Kent, F.G.S. 

 2-5628 . 2-5862. It scratches quartz. 



The characters detailed in the preceding sentence induced 

 the suspicion, — and which I communicated to Messrs. Tripe 

 and Cole in my first letter to them on the subject, — that it is 

 only a pseudomorphous mineral. 



Whether such be its real character, or whether it is to be 

 considered a new mineral, its primary form (assuming the 

 planes P and k /t' as primary) is an oblique rhombic prism, 

 differing less than one degree from the proportions of a right 

 rhombic prism, and of which the lateral planes meet at the 



* Communicated by the Author. 



angles 



