248 PROCEEDINGS OF THE AMERICAN ACADEMY 



ties contained portions of oxide of iron, probably derived from the de- 

 composition of iron pyrites, have led some to regard them as pseudo- 

 morphs of sulphuret of iron. But there seems to be no good reason 

 for ascribing any such forced and unnatural origin to these beautiful pro- 

 ductions. On the contrary, they seem to have been formed under the 

 ordinary circumstances of crystallization, either in open space, or while 

 surrounded by a matrix so soft and accommodating, as to allow them full 

 freedom to take the form it was intended they should take. Were the 

 crystals cubes, there might be some reason for regarding them in the light 

 of pseudomorphs of iron pyrites, because this is the most common form 

 of pyrites, and, moreover, all the pyrites hitherto brought from Califor-, 

 nia have been in that form. But, we may well ask, who has ever seen 

 even a cubic pseudomorph of gold ? Crystals of gold are rare, cubes 

 particularly so, and yet this form, on account of its simplicity, is made 

 the primary form ; whereas it would seem as reasonable, in cases of 

 the regular system, to select that form as the primary which is most 

 commonly and perfectly presented by the mineral, provided there is 

 no cleavage to guide us in the determination ; and there does not ap- 

 pear to be any, well made out, among most of the native metals. By 

 assuming those which most commonly occur in nature, we seem to 

 recognize a sort of inherent disposition, a preference, as it were, which 

 is shown by the mineral itself; and we avoid what seems to be a pal- 

 pable inconsistency, namely, the establishing of a cube as the primary 

 form of minerals which have never been known to occur under such 

 form, knd which even present a distinct octohedral cleavage. This is 

 the case with two at least. If we take the simplest form, the cube 

 should be made the primary of native iron, copper, lead, silver, and 

 mercury ; and so of some others, which occur in octahedrons and are 

 not determined by any certain cleavage. In the case of copper, some 

 authors have made the cube its primary.* Haiiy {Traiie, 1808) 

 even expressed his doubts as to the existence of cubic gold, while he 

 cites examples of the octahedron ; and Beudant (Mm., 1832) says 

 they are very rare.t Mohs implies the contrary, for he says {Min., ed. 



* They differ in regard to silver and iron, feome adopting the cube, and others 

 the octahedron, as the primary. 



t Cronstedt, in his Mineralogy, says, " I have procured in Transylvania a 

 specimen of cubic native gold, but 1 have never seen it anywhere else." In 

 Levy's enumeration of the splendid Turner collection formed by Henry Heuland, 

 eight examples are given of the regular octahedron, and only two of the cube, 

 one of these being from the very locality Cronstedt speaks of. 



