318 Mr Haidinger s Description of Edingtonite, 



of such as have parallel faces. Perhaps pyramidal felspar 

 also belongs to this class. There is a variety of it in the pos- 

 session of Mr Nordenskiold, from Pargas in Finland, which 

 shows the form represented, in Fig. 14, having only one of the 

 apices disengaged.* This kind of distribution of faces is, 

 however, quite different from that in the Edingtonite, from 

 which it likewise considerably differs in its angles, though the 

 specific gravity of the two substances, and their cleavage, are 

 nearly the same. 



3. Edingtonite occurs in crystals, the largest about two 

 lines in diameter, implanted upon crystallized Thomsonite, in 

 the Kilpatrick hills, near Glasgow. It is accompanied by 

 calcareous spar, and a curious variety of harmotome, (the pa- 

 ratomous Kouphone spar of Mohs,) in twin crystals, of the 

 form Fig. 15. In these, the faces of the four- sided pyramids, 

 visible in most other crystals, have entirely disappeared, and 

 the re-entering angles at the summit are produced solely by 

 the faces of a horizontal prism. It may be considered in this 

 respect as the last term of a series of varieties, some of whose 

 members were first described by Professor Weiss, -f- The 

 crystals of the Edingtonite itself are far from possessing such 

 a degree of perfection, that the angles given above could be 

 regarded as anything more than approximations, although 

 their general form is well defined. They resemble greatly 

 certain varieties of prehnite and felspar, but we must wait 

 for the discovery of other varieties of it, which may afford a 

 more extensive knowledge of the species, to enable us to de- 

 termine the genus in the Order Spar of the system of Mohs, 

 to which it might be referred. 



Analysis of Edingtonite. 



It yields water when exposed to heat, and becomes at the 

 same time opaque and white. Before the blow-pipe it fuses 

 into a colourless glass, though a pretty strong heat is neces- 

 sary for that purpose. 



Muriatic acid acts upon it, separating silica in a gelatinous 



* Mohs' Treatise on Mineralogy , Transl. vol. ii. p. 265. 



•f Magazin der Getelhchqft natirrfbrschender Freunde zu Berlin, viii. 33. 



