Crystalline Forms of Haytorite. 305 



I cannot but express my surprise, how any person who has 

 seen the crystals which are now before me in their combined 

 and in their separated state, could for one moment suppose 

 that they were pseudomorphous ones, modelled upon any other 

 mineral. 



There is yet one supposition which remains to be made, 

 namely, that the boracic acid, the characteristic ingredient of 

 Humboldtite, may have somehow or other been present with 

 the chalcedony, and determined it to assume corresponding crys- 

 talline forms, in the same way as M. Beudant (see this Num- 

 ber, page 291,) found that the presence of nitrate of soda 

 determined nitrate of potash to assume its crystalline form. 

 Without asking what has become of the boracic acid, we may 

 state that the crystalline structure which it superinduced would 

 appear in the interior of the crystal, as well as in its exterior ; 

 and that the crystal could, in no sense of the word, be called a 

 pseudomorphous one, because it is formed by the usual laws 

 of crystallization. Such a crystal would also have physical 

 properties different from those of chalcedony, in the same man- 

 ner as the nitrate of potash, altered by the presence of nitrate 

 of soda, has its physical properties changed along with its form. 

 But as no such variation of character appears in the chalcedony, 

 and as no circumstances whatever render such a supposition pro- 

 bable, we must abandon it as untenable. 



Although I trust I have now established to your satisfaction, 

 what indeed was your own idea as well as that of Mr Cole, that 

 Haytorite has not been modelled upon any other mineral body, 

 whether known or unknown, yet we have only increased the dif- 

 ficulty of accounting for its crystalline forms by the exclusion 

 of that hypothesis. 



The existence of perfect crystalline forms, without any trace 

 of internal crystallization, nay with an internal structure, in 

 which the axes of the elementary crystals have every possible 

 direction, seems a paradox in mineralogy. The subject there- 

 fore deserves the minutest investigation, and will amply reward 

 the labours of those who have time and talents for such an in- 

 quiry. It may not be unimportant, however, to mention, that 

 I have observed in many crystallized minerals a deviation from 

 parallelism in the axes of their elementary crystals; andit remains 



VOL. VI. NO. II. APRIL 1827- U 



